iLife suite is a must if you haven't got it. That gives you amongst other things iMovie & iPhoto which are brilliant programs for the novice to use to do movie and photo editing.
Depending on what sort of work you do then you can get Microsoft Office for Mac. Although Apple do the own version called iWork which is good once you get to used it. Keynote (PowerPoint equiv) wipes the floor with Ppt. However some of the transitions etc that it does won't display on ppt. So if you do a fancy presentation you will have to take your mac with you which is what I do.
If you get stuck on OSX say for example in the system preferences and you can remember the name of it under windows. At the top right corner of the window you see a search box with a magnifying glass in it. Type the windows name in it and it will highlight the correct option in System preferences for you.
Learn how to use
Automater. You can set this to do almost anything and saves you masses of time.
Look at the apple tutorials on the Apple website. They will get you started on the basics of most stuff on the OS.
Once you get a bit more savvy then you can look at other programs. These are what I have an recommend:
ONYX - Free Program - keeps mac running in peak condition. Use it once every 3 months or if you feel it's slowing down on start up and app start up.
Aperture 3 - £169 last I looked - Apple version of Photoshop. I have both and think Aperture is a more accomplished product. Especially as it is easy to sync your iPhoto library across leaving iPhoto intact and you can edit the copies in Aperture.
Delicious Library - £35 iirc - uses the iSight camera to scan a barcode from any DVD,book,cd,gadget,game etc and catalogues.
VLC - Free - same as on windows plays near enough anything.
App Zapper - can't remember price - use it to delete any app so you don't leave anything behind.
UnrarX - think it's free - same as winrar.
VMware Fusion - £60ish - for running Windows in a Virtual Machine if like me some work stuff only runs on windows. Same for things like VCDS, Etka etc.
VUZE - free I think - torrent download program.
Skype - free - obvious
Steam - free - if your a gamer.
Toast 10 - can't remember price - for burning DVD,cd etc
Realplayer - free - incorporates realplayer downloader which is great for Xhamster, youjizz etc (allegedly
)
StuffIt expander - can't remember price - if unrarx doesn't open it this will.
Use
Time Machine - awesome utility, gives ability to recover anything from a single document to the whole OS including installed apps.
You don't necessarily have to book into those lessons with Apple (although they are very good) if you have a specific problem and no-one can help you can go to any genius bar and they will show you pretty much there and then how to achieve what you want.
I'm always happy to help where I can as well.