I just got a MacBook pro and it's my first encounter with MacOS so I wanted to ask - does anyone know good applications I should look into? Any must-haves for Mac users?
I am almost exclusively a Mac user (actually, Apple systems in general, as I had an Apple ][e growing up*), so my first question to you would be: What type of applications?
In general:
-Web browsing: Safari is fine, but I find it slow. I usually use Camino (a Mozilla offshoot) as it is much faster. Plenty of people like Firefox, although I've personally never been a fan.
-Office products: I generally end up using MS Office, just because it's become the de facto standard. I've been using Keynote (part of iWork) for presentations instead of Powerpoint, though. I like the presenter features it offers (seeing slides in advance on the monitor with notes, etc.). Also keep in mind that you can save files as PDFs natively, without having to invest in external PDF software.
-Compatibility: Boot Camp is built into the system these days if you want to boot into Windows (which is what I did when I wanted to play Portal). For virtualization, I use Parallels so that I can run the Windows-only scientific applications we have in lab. It runs concurrent with OS X, and integrates itself quite well. Crossover (based on WINE, so you don't have to boot Windows at all) is getting better, but still slow for a lot of applications.
-Other: Photoshop is pretty ubiquitous these days. What else can I say about that?

Things like VLC and Mplayer are also available should the native Quicktime not meet your video-viewing needs. Also, KoL Mafia, but that's a necessary app...
A good resource for application ideas is Versiontracker (
http://www.versiontracker.com/ ). Browse the categories to get a sense of what's out there. If you have specific application needs, I can probably point you in the right direction.
The MacBook Pro is a mighty beast (that's the portable I have), so you should enjoy it.
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* I have, over the years, owned an SE/30, an LC, a 6115, two UMAX SuperMac clones (the C600 and the S900), a PowerBook G3, and a G4 MDD tower--frequently modified and upgraded in strange power-tool requiring ways; also, I worked with a host of other models while a computer lab consultant in college.