I agree with m2kio that anti-virus and anti-spyware software is largely unnecessary on a Mac so far. In fact, as on Windows, there have been reports of such software causing problems (data loss, system instability, slow performance, etc.) rather than fixing them. However, be aware that Macs can be "carriers" of things like Word macro viruses, email viruses, etc. and such software would catch such things so a Mac won't unwittingly spread them.
The firewall software built into Mac OS X is
ipfw. It is a simple thing to configure it through the System Preferences (Sharing -> Firewall). Here's
an article on O'Reilly's MacDevCenter.com that shows some more advanced configuration options.
With respect to OpenOffice, the best version to use on Mac OS X is
NeoOffice/J. It doesn't require X11 and its interface is much better integrated with native Mac apps and the Mac look-and-feel. Basically, OpenOffice.org had intended to "nativize" OpenOffice for the Mac, but 1) it was a lot of work, 2) there weren't really enough developers willing to devote time to it, and 3) NeoOffice/J, which was originally intended as a testing ground for ideas and techniques for nativizing OpenOffice, had advanced to the point where it was preferred by users. So, NeoOffice/J was dubbed the best choice for Mac users and OpenOffice.org put off the task of nativizing OpenOffice itself into the indefinite future.
A good, but very simple, image editing program is the shareware program
GraphicConverter. As its name implies, its main purpose is to convert graphic files between many different formats. However, it also includes basic image editing tools, as well.
In addition to
http://www.versiontracker.com, there is also
http://www.macupdate.com and, of course,
Apple's third-party downloads section.
Also, in addition to
VLC, there's also
MPlayer OS X.
