iTween is a simple one file drop in for some great scripted animation and easing that is very reminiscent of Flash using Penner equations and common libraries so it is easy to get started. It works for web player, desktop and iPhone Unity (however long that lasts).

Some sample code looks like this:

private GameObject go;
private GameObject cam;
 
void Awake()
{
    go = gameObject;
    cam = Camera.main.gameObject;
}
 
private void Start()
{
    iTween.rotateFrom(go, 1.5f, 0, null, 90, null, iTween.EasingType.easeInExpo);
    iTween.moveFrom(go, 1.5f, 0, null, 3.5f, null, iTween.EasingType.easeInExpo);
    iTween.colorTo(go, .3f, 1.5f, 3, .5f, 1.2f);
    iTween.shake(cam, .8f, 1.5f, null, .3f, null);
    iTween.scaleTo(go, 2, 2.3f, null, 2, null);
    iTween.rotateBy(go, null, 4.3f, .5f, null, null);
    iTween.moveTo(go, null, 4.6f, null, 1.2f, null);
    iTween.moveTo(go, null, 5.8f, null, 0, null, iTween.EasingType.easeInExpo);
    iTween.shake(cam, .8f, 6.8f, null, .3f, null);
    iTween.colorTo(go, .5f, 7.6f, .165f, .498f, .729f);
    iTween.scaleTo(go, null, 7.6f, null, 1, null);
}

• Download Javascript iTween by Bob Berkebile (pixelplacement.com)
• Download C# iTween by Patrick Corkum (insquare.com)

Basically these engines look to be micro and provide pretty nice features while being so small. Micro tweening engines like GTweeny (3k), ByteTween (1.7k), TweenLite (2.7k), TweensyZero (2.9k) and Tweener (9k) have varying levels of support of features (Tweener being the most loaded with color and filter support without other kits just init, also TweenLite with a nice configurator to include only what you need).  Micro kits have benefits when used for banners, animated assets (where you have many assets and the per asset savings is worthwhile) and other places you just want really small output.

Light Transition ByteTween

(1.7k)

This kit has a c# version as well as a small as3 bytetween version.

The ByteTween static class eats only 1.7K of compiled clip! With this size it supports:

• Creation of tweens of any numeric property (not color/uint properties).
• Pause,Unpause,Cancel operations based on the tween target and property.
• Overlap system that cancel tweens of same property in order to avoid erroneous behavior
• Alpha tween with negative alpha support (negative alpha sets the MovieClip visibility to false)
• ’scale’ tween of both ’scaleX’ and ’scaleY’ properties.
• OnComplete callback with any number of parameters
• Easy interface for creating new tweens!

Download light_transition_CS_0.5a.zip.zip (c# version)

Download thelab_ByteTween.zip

TweenLite

(2.7k) base

• SPEED – I’m not aware of any popular tweening engine with a similar feature set that’s as fast as TweenLite. See the speed comparisons yourself.
• Feature set – In addition to tweening ANY numeric property of ANY object, TweenLite can tween filters, hex colors, volume, tint, saturation, contrast, frames, and even do bezier tweening, plus LOTS more. TweenMax extends TweenLite and adds even more capabilities like pause/resume, rounding, event listeners, timeScale, and more. Overwrite management is an important consideration for a tweening engine as well which is another area where the GreenSock tweening platform shines. You have options for AUTO overwriting or you can manually define how each tween will handle overlapping tweens of the same object.
• Expandability – With its new plugin architecture, you can activate as many (or as few) features as your project requires. Or write your own plugin if you need a feature that’s unavailable. Minimize bloat, and maximize performance.
• Management features – TweenGroup makes it surprisingly simple to create complex sequences and groups of TweenLite/Max tweens that you can pause(), resume(), restart(), or reverse(). You can even tween a TweenGroup’s “progress” property to fastforward or rewind the entire group/sequence.
• Ease of use – Designers and Developers alike rave about how intuitive the GreenSock tweening platform is.
• Updates – Frequent updates and feature additions make the GreenSock tweening platform reliable and robust.
• AS2 and AS3 – Most other engines are only developed for AS2 or AS3 but not both.

Download TweenLite

TweensyZero

(2.9k) base

Here are some simple steps to help you get started with creating your first animations with TweensyZero. TweensyZero is a light weight version of Tweensy most core features found in Tweensy are available to TweensyZero. Documentation for TweensyZero can be found under the folder ‘documentation/zero’ or online

Download TweensyZero

gTweeny

(3k)

gTweeny is gTween‘s lightweight younger sibling. It strips a lot of the secondary features of GTween (proxy, timing modes, etc) in favour of smaller file size. It is currently under 3kb…

Download gTweeny

Here is a list of all open AS3 “Micro” Tweening engines < 5k

• ByteTween (1.7k)
• TweenLite (2.7k)
• TweensyZero (2.9k)
• gTweeny (3k)
  

Here is a list of all open AS3 Tweening engines and base kits

• Animation Package
• AS3 Animation System 2.1
• AS3Easing
• Go (base animation kit – create your own tween engine)
• gTween
  
• KitchenSync
• Twease
• Tweener (9k)
• Tweensy
• TweenLite (TweenMax)

The decision on which to use can be affected be features you want, how it feels (many use the same object syntax so it is dynamic), what performance do they have (all are orders of magnitude faster than the built in tween (flash) or transitions (mx/flex)), which size is ok, author/community support needed (some are more active than others adding features or simplifying and tweaking performance methodically), and many other factors.  There are definitely plenty to choose from.

Speed Tests for many Tween Engines

• Green Sock Tweening Comparison Tool
• Moses Benchmarking Tool (relative comparison against SimpleAS3Tween sample)

For more on each features see their sites or these previous lists on tweening engines:

• Updated: List of Best Animation Packages for AS3

Additional Features

gTween has a lot of additional features. I’m not going to write about all of them, but here are a few:

• autoHide, sets the target’s visible to false when the tweened alpha is 0
• autoReverse, reverses the tween when it ends (and plays it backwards if autoPlay is true).
• smartRotate, rotates in shortest direction
• supports using setSize for tweening height and width on components
• support for updating properties like matrix and colorTransform automatically during a tween.
• jump to any point in a tween by setting position.
• loop a tween by setting nextTween equal to the same tween.
• determine the state of a tween with the state and paused properties.

Download (Beta 1)

To access the API documentation, and download the latest build of GTween, visit the GTween page at gskinner.com/libraries/gtween/.

Here is a list of all open AS3 Tweening engines and base kits

• Animation Package
• AS3 Animation System 2.1
• AS3Easing
• Go (base animation kit)
• gTween
• KitchenSync
• Twease
• Tweener
• TweenLite (TweenMax)
  

Tweener and TweenLite have become the micro animation kits as well as micro kits you can make with Go base kits. TweenLite, TweenFilterLite and TweenMax divided up into different kits allows it to be embedded for banners or small assets easier if you don’t need the filters or other advanced tweens (this comes into play heavily with large games and asset collections when the compiled SWF each need the library). Tweener packs all features into one kit for simplicity. GreenSock kits are divided up for need. The comparison together is about the same but for basic tweens TweenLite is only 2k.

Performance is one area that the kits from GreenSock have really shined and since the addition of the speed tests and benchmarks it has become a great focus on showing how the open source kits are much better than bloated included animation calls in Flash and Flex defaults. I think all the kits have niches that they fit and Tweener and TweenLite are just very simple to use which adds alot to an animation kit success.

List of Animation Kits for AS3 (some for AS2 as well)

• Tweener
• GreenSock
  • TweenLite
  • TweenFilterLite
  • TweenMax (Speed Test)
• Go Base
• Twease
• AS3Easing
• Animation Package
• Animation System

If you are using the Flex of Flash default animation classes, I am sorry…