Starting with not an app. An external hard drive for Time Machine. You need to backup as often as possible. Might I recommend any of the Western Digital MyBook external drives. Shoot for the dual-interface model if you can (Firewire and USB). Firewire is better on the Mac. And Faster. And, you can boot to it.

If you want a backup solution other than Time Machine, I would recommend SuperDuper. $30 and worth every penny.

We will begin with the free apps.

Before you do anything else, get a copy of Quicksilver (free) and install it. If you used the ‘run’ box in Windows (or many keyboard shortcuts), you will use this all the time. After it is installed, go into System Preference –> Spotlight and uncheck menu keyboard shortcut at the bottom. Then, whenever you press cmd-space, Quicksilver will come up and be ready.

For video, you will need Flip4Mac and Perian. Download and install both of them and you will be able to play any video you come across. Another good one to have is the VLC Player. This app plays everything, but I only use it to play the odd video files that quicktime won’t (high def .mkv files in particular). And, if you are one that likes to rip your DVD’s to your machine, Handbrake is the only way to go.

For IM, iChat works very well, but it is limited to AIM users mostly. If you need to use Yahoo, MSN, gTalk or Jabber, you are gonna need Adium. If you need to video chat with Windows users (yahoo or MSN) you can’t. But, you can with Skype.

As for browsers, you have many many choices. The Mac does come with Safari, but if you are switching from Windows you will hate it. Likewise you will hate Firefox 2 because it is very slow on the Mac. If you are downloading today, I would recommend Firefox 3 RC1 RC2 and get the full version when it comes out next month. You could also try Camino, but you might get laughed at. Oh yea, Opera runs here too, as does Flock.

For email, everyone swears by mail.app, but I’m not a fan. I’m also a gMail user. But I have tried Mozilla Thunderbird on the Mac and it works like it does on Windows.

If you have to log into a windows machine, I would highly recommend Remote Desktop. Sure it’s a M$ app, but it works very well and it’s free. You get file transfer and clipboard access, plus remote printer access as well. If you need to use VNC, you are stuck with the horrible Chicken of the VNC. I say horrible, but I’m used to the much more feature-rich VNC clients on Windows like Ultra (not available for the Mac).

For FTP, there are a bunch. Filezilla on the free tip is popular, as is Cyberduck which I’m not a fan of. Beside the avian icon it brings, I found it to be less than stable. If you don’t mind paying a few bucks, I will highly recommend Transmit by the good lads at Panic Software. $30 and it works great, plus integrates with Quicksilver nicely.

Finally, unless you absolutely have to have Microsoft Office, try to get ‘08. ‘03 will be cheaper but it’s slow. If you are thinking OpenOffice, don’t. They are working on an official port or you can try NeoOffice for native support. But it’s slow and cumbersome. If you don’t need office, for sure go with iWork. It’s cheaper, faster and works quite well. You will have to do a bit of re-learning like everything else on the Mac, but you will find it’s worth it.

If you are going to do any video editing or need to convert from one video type to another, you will have to get QuickTime Pro ($35) from Apple or Visual Hub. I recommend VH here because it supports a wide range of files and it’s fast.

Of course this is far from a complete list. But it should be enough to get you going. Of course you are going to want to keep an eye on the comments since I’m pretty sure the other w(t)f readers are going to want to chime in.