CyanogenMod 9 may feature Cornerstone Multitasking, Run multiple apps side by side on your Android!
The best aftermarket Android firmware CyanogenMod become famous for it's stock android feeling with lot of customizations, hacks and tweaks. Currently the team working hard for CM9 based on the latest Android 4.0 Ice Cram Sandwich. Since Android 4.0 is such a major change from 2.3, they want to give CM9 a look and feel like your device should have come with CM9.
We should clarify, this is experimental, and not guaranteed to be mainlined into CM. If it is done, it needs to be done right and not break apps all over the market or be a nightmare to upkeep down the line.