For general file sharing, <a href="http://www.kazaalite.tk/">Kazaa Lite</a> is the way to go.
For text editting, I say <a href="http://www.textpad.com/">TextPad</a>. It's what I like: tons of useful features for power-users, but uses little memory and is very responsive.
And who could forget the best IRC program ever, <a href="http://www.mirc.co.uk">mIRC</a>.