I just went through Macworld's November 2005 issue and downloaded a few useful things:

Safaributtons replaces the Safari "Bug" button with a "New Tab" button, so now I can open a new tab using one click rather than having to CTRL-Click in the tab bar (useful when I only have one hand to use on the mouse because the other one is captured by a cat).

SafariSource is a plug-in that gives the "view source" option context coloring, very helpful for reading source files when you're trying to find something specific.

Taboo gives you a dialog box that asks you if you really want to close Safari, and all the tabs that you had open, if you try to close it when multiple tabs are active.

Cliplite is a dashboard widget that lets you store multiple clipboard items -- text, images, all kinds of things.

And finally, TreetopLights puts a Christmas tree on your desktop and holiday lights around the screen edges. You can remove the lights, which I did, and just have the Christmas tree.

Paparazzi is a small utility for Mac OSX that makes screenshots of webpages. That is, the whole webpage, not just the portion that you can see on your screen. So when you have a really long page that you would like to capture, rather than making several screenshots and sticking them together in Photoshop, you can make it in one fell swoop, and save it in any of several formats. Very cool. It can also make a thumbnail automatically (below).