To Jailbreak your iPhone 3GS follow BigBoss's guide @ 3gs jailbreak released and guide help for install | iPhone News, Help and Guides

Working:
Notifier
SBSettings
Lock Calendar
WeatherIcon
mim
mcleaner
categories
haptik pro
123spoof
memtool
appsync

Not Working:
qTweeter, crashes to safemode
Finder
cyntact
winterboard

source: Cydia Apps that work on 3GS 3.0 - xSellize

Working (Semi):
- Status Notifier
- Small icons in taskbar update and show, application crashes upon clicking.

Currently backgrounder is also working for me.

Is the Gekino 5 icons Dock working?

iBluetooth is not working, also crashes the stock bluetooth drivers and requires a reboot to reenable them.

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Terminal.app 'more or less' works.

Firstly you really need RC2 of the purplera1n jailbreak, otherwise it's seriously screwy.

With RC2, the app starts upside down (WTF) - you can then rotate the phone twice to get the screen the right way up.

Prefs don't seem to stick - you can change the font colour to green (for example) and it will work, but any reset of the screen (e.g. running top and then quitting it) will return to white text.

The pie menu appears to work but I haven't replaced all of my customisations yet, simply because I'm expecting a bunch of app updates to eventually appear, since v3.0 has enough differences to mess up many of the Cydia apps and I'm sure their authors will update in due course...

5 icon works.

Working:

Intelliscreen
Winterboard

Not working:
Rotation Inhibitor for SBSettings

imobilecinema works just as good as any beta.

an interesting fact though, combined with yxflash plugin, it'll stream different formated videos online in flash player.

With this, I am pleased.

Edit. Hulu, veoh, and kumby doesn't work and todou, and megavideo sorta work, restarts the video sometimes though or no sound/picture or both (still has a lot of bugs to it). Just have to wait for buffering on other sites. Can't wait till a new update comes out for the two.

As per my other thread, VOIPover3G definitely NOT working. Very annoying.