Here is a funny experiment with javascript. It takes normal text as input and returns encoded ASCII text (from 0x20 thru 0xFF) with a 30% reduction in length, which can be decoded later to the original, with some exceptions/rules. It preserves only alphanumeric characters (except for some of them which are transliterated specially, like 1 = I or Z = 2).
This could be funny as a workaround in some situations, like circumventing the classical Twitter limit of 140 characters (would need the decoder on the other side, of course).
Julio Sancho's Blog 