I’ve been indulging my inner geek with:
Ask 500 People, it’s a polling tool mashed up with google maps, anyone can ask a question and anyone can reply. Results are plotted on a googlemap, and you can see aggregated score. Each poll runs until 500 people have answered. I’d put one on here but WordPress seems to be allergic to javascript at the moment.
Blist, it’s what spreadsheets ought to be, you can include checkboxes and ratings, URLs get a snap view on them. Take the tour and play with it, it’s fun.
Monkey Brain, OK, not really totally geek tool, but more an outlet for excess opinions
Gimp, an image editing tool. I’m used to working with photoshop so it was pretty easy to start with. It’s fun, so far I’ve made the invitation for a party and that’s it.
Netvibes, make your own portal of tools, games, RSS feeds. It’ll pick up your gmail and your del.icio.us feeds.
Library Thing, I’m a bit scared to start with this, I suspect that this cross over between books and geekdom is likely to be very addictive very quickly.
Sxipper Uses open ID platform so I can forget my passwords. It’s the best thing since sliced bread except that it’s only supported on Firefox and at work I am forced to use IE.

Gimp is ok, for a blogger for instance, who needs to do quick edit and simple image editing. Photoshop still rules.
Netvibes is ok, but IGoogle does the same, has tabs too and I prefer its layout.
Agree on Gimp, it’s been OK for stuff I do privately. I still have photoshop on my work machine so I won’t buy it for home use.
I’ve looked at iGoogle and it’s also fine, does pretty much the same thing. I might have an irrational preference for the new guy on this one though. I’ll stay with netvibes.