Marts - get rid of BossPrefs - it's out dated and discontinued. Download SBSETTINGS instead. It's the BossPrefs replacement, and doesn't use a spring board icon. You swipe the status bar (either on springboard, or in an app) and it drops down;
I can't be arsed to list AppStore apps - I've got loads and they are easily findable
Some of the Jailbreak apps I have installed that are usefull; (all from Cydia)
WINTERBOARD - used for applying themes and visual changes to the phone
CALLFORWADING - Removes the annoying "call forwarding" bubble T-Mobile users get when making calls
WEATHERICON - Changes the stock weather icon to show real time weather and temperature
MXTUBE - Allows downloading and saving of YouTube video's, aswell as allowing streaming over the 2G network (which YouTube can't do, only 3G or wifi)
STATUSNOTIFIER - adds icons to the status bar when new mail, mms, sms, missed call are recieved
SAFARI TAB CLOSER - allows you to close all tabs in Safari with one button
SWIRLYMMS2 - MMS for iPhone 2G
Rest of the stuff is just tweaks, themes, etc etc. A cool one is "PERCENTAGE BATTERY" which looks exactly like the normal battery (on the lockscreen, when charging) but shows a percentage in numbers;
One I'm missing tho is "NOTIFIER WIDGET", which was an extension for STATUSNOTIFIER, and added text to the lockscreen;

(not my phone, but the Status Notifier icons are up top in the status bar, and the text on the screen is the Notifier Widget)
For some reason, it's still not been updated for 3.0 yet