These are my favorite tweaks for my JB iPhone 4. A lot of them would be great to have on an iPod Touch as well.
Activator (Activate apps with gestures)
BiteSMS (SMS app, allows features not available in regular SMS app)
GlasKlart HD (Theme)
OpenSSH (Allows SSH to phone)
SBSettings (Gives quick access to settings anywhere on the phone)
Serious SBSettings HD (Theme)
FolderEnhancer PAID (Unlimited apps in folders, folders in folders, pages in folders.)
Five Icon Dock (Five icons on dock)
Celeste HD (Theme)
Winterboard (Used to theme iPhone)
TV Tube Sleep PAID (Cool animation when putting iPhone to sleep)
SnapTap PAID (Take pictures with volume buttons)
FakeClockUp (Speeds up animations)
Remove BackGround SBSettings(SBSettings Add-on. Kills apps in multitasking tray)
Typophone 4 (Lockscreen theme)
Lockscreen Clock Hide (Hides lockscreen clock)
Nexus S Live Wallpaper (Theme)
MobileVolumeSound (Gives Mac volume sounds)
Barrel PAID (Cool animations when switching pages)
Graviboard PAID (Makes icons move around screen with gravity)
Analock HD (theme)
iFile (Browse iPhone file system)
vWallpaper (Video wallpaper)
Classica 3 (Theme)
Suave HD with icon packs (Theme)
Avant 2 HD (Theme)
biteSMS to Retina SMSimage icon (Gives BiteSMS retina icon)
Notifier+ PAID (Status bar and lockscreen notifications)
Edge Binding SMS (SMS Theme)
iLock PAID (Draw pattern to unlock)
I would recommend looking up some Youtube videos on the ones you are interested in.