I promised to make a list of the most used non-prof apps for a friend, and how to install's them, for a newly converted OS X user friend (with Windows and various Linux background). But maybe it will be useful for some others too, so here we go.
CD and DVD burning
You can use
Finder,
Disk Utility (in Applications / Utilities), or
Toast (not freeware), or
FireStarter FX (free).
Browsing & Email
Safari is pretty good (came with your system), but you may want to try
Camino or
Firefox too. An alternative to mail.app of OS X is
Thunderbird, which now probably has better Addressbook integration. And
Shiira is based on Safari, also worth a try (some more possibilities).
Messengers
AdiumX (free) has AIM, iChat (.mac), ICQ, YIM, msn, Apple Rendezvous, anything you want and you can have multiple accounts on each service, and you can make the gui look exactly as you enjoy. There are a few other alternatives too -
Fire (free),
Proteus (shareware, works as well free). iChat is of probably enough for you if you use only AIM or iChat messenging, but at least AdiumX is worth a try. And for voice chats and free telephony, try
Skype for talking for people with ANY operating system, or via phone. Currently Skype seems to have better audio quality in less than T1 bandwidth than iChat.
Privacy
Privoxy and
Tor (bundled to Tor, freeware) may be worth a try. I have home issues with that since I am too lazy to open port 8118 in the wireless base.
For encryption needs, I would suggest
GPG (GnuPG), basically a free replacement for
PGP.
Macgpg is the best and easisest for OS X. (In short: first install GNU Privacy Guard, then PGPreferences, then GPG Keychain access, after that you do want to install
Sente.ch mail.app plugin - done it all in that order makes it work, so 30 minutes of maximum hassle, and you have encryption).
Thawte is another way of obtaining a free digital certificate, and probably easier to use. If you attach your digital signature to your emails, and have the signature of someone you will send email to, you can encrypt with thawte as well.
Other apps
Subethaedit is a nice free code editor / notepad, with which you can edit the same code with your friends over bonjour/rendezvous or internet.
iJournal is a nice editor for LJ, or for generic a href type editing, faster than coding manually for sure - also
XJournal seems to be nice.
Search at Apple's site is your friend for trying to figure how to do something with OS X.