Not sure anyone posted this before
A tutorial to speed up your ipod touch
http://www.ipodtouchfans.com/forums/showthread.php?t=224341

I have tried on mine, boots faster and snappier now

ipod touch 2g has a built in speaker. there's no 8gb 3g ipod touch
features wise, there's no difference afaik
hardware wise, 3g has better processors and graphics renderer or something

Direct procedure to JB with blackra1n

1) Update to 3.1.2 if you haven't
2) Connect the touch to PC
3) Run blackra1n -> make it ra1n
4) Don't do anything and wait for reboot
5) after reboot, go to the app "blackra1n"
6) install cydia/rock/icy

and, you're done