It's been (about) 4 months since I got my MacBook Pro, and here's a quick rundown on the software I've found, and even in some cases paid real money for, since then.
Adium chat client - accesses my MSN, Yahoo!, Google Talk, and most importantly for me, Lotus Sametime chat lists. Full featured and robust with good notifications
Scrivener writing application - ties research, notes, ideas and writing all together. Time to dust off my novel drafts and get them back on track [props to Ryan Chase for passing this one along]
Apple mail client - the integration with Gmail's IMAP capability has made this my main mail client (outside of work, where -- shudder -- Lotus Notes is mandatory).
Alphababy - this locks out your keyboard and trackpad, and turns every key into a letter/shape generator for kids. Awesome fun for those under 5.
Unisudoku - Gets my Sudoku fix fixed. I even paid money for this, so you know it's gotta be good.
That's enough for today. I'll post more another day.