I just did this and went from 69mb to 101mb free!
I used root explore to move the dalvik-cache to /cache
I got this from this post in the forums.
Member Nick7
Device(s): LG crOptimus S
ROM/Kernel: Nameless ROM Location: Chicago
Join Date: Dec 2010
Posts: 790
Thanked 477 Times in 126 Posts
Activity:
[MOD] Move dalvik-cache to /cache STOCK ROM ONLY
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**THIS WELL ONLY HELP YOU IF YOU ARE ON A STOCK ROM. **
**THIS OVERWRITES ANY KERNEL YOU HAVE.**
Dalvik-cache to /cache mod frees up some space on the data partition for more applications. I bumped from 120mb free to around 160 mb free.
After having a bunch of trouble using pre-made scripts posted around different forums, I decided to try a different method and edited the init.rc in boot.img.
Anyways, flash this zip in Recovery. After the first boot is complete, reboot into recovery and clear dalvik cache. Now you should have some extra space to work with.
v2: better method, proper kernel lol..