re: Official iPhone/iPod Touch owners thread
Cydia often crahes due to memory leakage but if in your case if it's too often, I would suggest you to jailbreak again (you may also try out a few very good suggestions already made in this thread) cuz cydia is indispensable app to have.
As for adding apps that you downloaded through torrents. Normally, these are DRM stripped pirated apps and there is a way but I would rather not help you cuz it's not fair to developers working their a$$ off and is against forum rules as well. However, if you still want to do the same, google is your friend. Also there is a possibility some idiot put it there just by ssh'ing into his phone and copying .app files so they might not work even if you do everything right.
BTW I updated my iphone to latest OS 3.0.1 (sms patch release) and then jailbroke again . Everything seems to work fine as of now. Battery life is so good ever since 3.0 came and phone seems to be getting charged up quicker than before. If battery is still an issue for you guys, I recommend:
1. Getting onto 3.0 bandwagon.
2. Get rid of backgrounder app as it seriously depleted battery like anything. iPhone is not ready have that app.
3. Do not install active wallpapers.
4. Make it a habit to plug your iphone to you car-charger everytime you get in.
I have never been able to exhaust my phone's batteries and I use it heavily all day (stocks and ipod app). Of course playing NFS depletes battery entirely within an hour or two but I try to avoid that in office