I guess nowadays a person is defined by what can be found about them on the Interwebs. This should make it easier:

CiteULike

“CiteULike is a free service to help you to store, organise and share the scholarly papers you are reading. When you see a paper on the web that interests you, you can click one button and have it added to your personal library.” Not very social, but you can see what I’m reading, or at least citing.

Criticker

Criticker is a social movie review site. You rank a few movies and it tells you if you’re gonna like some other movie, based on what people with a similar taste in movies think. I only recently signed up there and still have a huge rating backlog – consisting partly of all the older and worser movies.

delicious

delicious.com, formerly del.icio.us, is a social bookmarking site. They have an excellent firefox extension which makes organizing, tagging, and finding bookmarks very easy. These are mostly private links, though some may be related to what I do at the university. I used to have a separate account for work-related links, but that’s more or less dead. They also have an RSS feed you can subscribe to.

facebook

the only social network I frequent on a regular basis

flickr

flickr is a photo sharing site. I’ll upload something to flickr every now and then when I have time to work through that huge pile of unprocessed shots on my hard drive. They have an RSS feed you can subscribe to, if you never want to miss any of my shots.

Google Reader

I use GReader to stay on top of my RSS feeds, for which it is probably the nicest front-end there is. I’ll share a link every now and then, mostly the funny stuff.

LinkedIn

Pretty much the same as XING, but seemingly more popular in the US. They have some nice apps integration, like TripIt. I briefly scan my weekly updates, but that’s about it.

studiVZ

studiVZ is such an obvious copy of facebook that it’s almos ridiculous. It is very popular among German students, though, so that my network there is probably the largest. I have a studiVZ account, but that’s about it. To find out what’s going on, better look me up on the original, facebook.

TripIt

TripIt is pretty cool. You forward your various travel-related email confirmations to TripIt and it builds you a trip itinerary. Publishes an RSS feed that can be used e.g. in Google Calendar, so that there’s no need to enter travel dates there separately. Also keeps you updated on where people in your network are going.

Twitter

No, I don’t tweet or tweedle or twittle or whatever.

XING

When I joined XING, it was still called OpenBC – that’s not too long ago, though. I’m more of a passive user, barely able to keep my profile up-to-date and every now and then looking to find people I know on a professional level there.