Here are the software for the one who new to Macintosh, if you are a prefessional Mac users please feel free to add to it.
Audio/Video Players and converter
iTunes -
Plays music and now videos. You already have it, you know it, I won't waste time here. Other full featured music players are hard to come by on the Mac because no one feels they can outdo iTunes, no ones sees a need and everything is already so well integrated with it
Quicktime -
The video (and audio) player for the Mac. with the right plugins you can make it do much more. More on that later. Upgrading to Quicktime Pro will give you a few nice editing features as well as a wide variety of output formats and settings, its good to have around
VLC -
The play it all player. If it won't play in Quicktime give this guy a try.
Mplayer -
Not used too much, but sometimes it may come in handy. Similar to VLC
Real Player -
You don't use this for much, but sometimes you need it. All I have to say about it is this -- It doesn't suck as bad as it does for Windows. Downloading it is still a pain though
HandBrackHandBrake is an open-source, GPL-licensed, multiplatform, multithreaded video transcoder, available for MacOS X, Linux and Windows.
Mac Video Converter Convert Video to iPod/iPhone/MP4/MKV with powerful movie editing function: support movie trimming, cropping, effect adjustment, multi-file merging, etc.
Mac DVD RipperIt can convert DVD to AVI, MP4, MPEG, M4V, MOV, 3GP, MPG, FLV, extract audio from DVD to MP3, M4A, AAC, WAV, OGG, APE, etc. It is the best Mac DVD iPod Ripper, Mac DVD iPhone Ripper, Mac DVD to Zune Ripper, Mac DVD to PSP Ripper.
Office (word processing, spreadsheets, presentations, etc):
MS Office -
The obvious one. Microsoft makes it, it will work flawlessly between Windows and OS X, probably the best choice for power users and those the often deal with multiple environments
iWork -
This is Apple's first step into a modern office solution (Appleworks was looking really dated). It consists of Page and Keynote, a word processor and a Powerpoint type application. Keynote is great, but Pages as a slight learning curve on it, especially if you come from MS Office
iWork does not have a spreadsheet application. however if you are looking for on that fits with the iWork style, give Tables a look
p2p
Acquisition -
This is the best looking, fastest, most useful P2P app I've ever come across. It uses the gnutella network, but also added support for torrents. However, if you don't pay the shareware fee is has some awful nagware, its a big turn off to most people that don't pay up front.
Acqlite -
A free open source version of Acquisition. It isn't quite as pretty of feature rich, but it gets the job done
Limewire -
If this is in your dock people will instantly know you're new to the Mac, but use it if you wish
Xtorrent -
The newest torrent app out there for the mac, from the same guy that makes Acquisition. Its free for now while in beta. It brings the ease of standard P2P apps to the world of torrents. Its nice.
Utilities
Disk Utility -
This is already on your system (/Applications/Utilities/). It will allow you to verify your disks, partition, create software raids, burn iso and dmg files to disk, repair permissions, etc. You can also (and sometimes need to) boot off your OS X install CD to run the app, it is located in the Utilities menu once the desktop boots from the CD
OynX -
This is a great all around utility. I can't even begin to go over all the funtions, it does system maintenance, interface tweaks, etc, etc. However, be care, it is very powerful and you can overdo it and mess things up if you aren't careful. There are scripts that run in the background on the Mac at 3am, if you computer is off they don't run, OnyX can run them manually to keep your system running smoothly
App Zapper -
The missing uninstaller. Now uninstalling an application isn't hard (just drag it to the trash), but if you want to get it all (which is normally just a small preference file or a folder) you can either use Spotlight, or do it the fun way with AppZapper. Just drag the app you want to get rid of onto it, it will find what needs to go and "zap" it. You'll be installing apps just to "zap" them
FontExplorerX -
If you are a pro, or just have a lot of fonts, you need this. Font Book that comes with the Mac kind of sucks for font management. Best of all, its free.
Quicksilver -
This is a hard one to explain. Think of it as part application launcher, part everything on your system rolled into one. It allows you to perform tasks with many of your apps without ever opening them. Its takes some time to learn, but once you do you'll work faster and easier then you ever though possible
Graphics
Photoshop -
Or I should actually mention the whole CS2 suite of apps. I don't think this needs a description
Graphics Converter -
I don't use it, but many swear by it. Give it a look
MacGimp -
The Gimp for OS X. If you're too cheep to buy Photoshop or are an open source fan this is the way to go.
Browsers
Safari -
Comes with the mac. Its the fastest browser on the mac, bar none. Use it for a week, you'll fall in love
Firefox -
I shouldn't have to tell anyone here about this
you know where to get it
Camino -
The mozilla folks made a browser just for the mac. The story I heard was that this browser gave them the idea for Firefox. If you want gecko with more of a mac style, this is it. Still needs some work imo.
Opera -
Yet another cross platform browser, and the true innovators of the web browser
OmniWeb -
You can tell this one was made for the mac, drawers, thumbnail tabs, etc, etc.
Shiira -
A Safari clone with lots and lots of extras. Its worth the download for the page turning effect alone. It never quite seems finished though
iCab -
Yet another browser
Other Internet Stuff
