Social Media
I'll admit that I wasn't an early adopter of social media (I didn't join Facebook until May 2009, hoping perhaps I'd be the last person on the planet to do so), but now I'm just not a user, but an advocate. I can't think of a single social environment or interaction that won't be affected by social media technology, and in many ways, enhanced by it. (Do you hear that, education? Don't ignore this stuff!)
blogs, big and small
Raymond Johnson @ downclimb
I've been blogging since 2001. I think I was even one of those pre-Google-acqusition "Blogger Pro" users who paid for extra Blogger features. My blog includes posts on all topics, but I try to tag each post to make catagorizing a little easier.
MathEd.net Blog
In October of 2009 I started a new blog for my thoughts on math, education, and math education. You're likely to find some talk about uses of technology in education mixed in as well.
downclimb on Twitter
I regret not joining Twitter when I first heard about it. My favorite description of how Twitter works was this: "Use Facebook to keep in touch with old friends, but use Twitter to keep in touch with friends you haven't met yet." These tweets automatically get posted to my Facebook account, so don't worry you'll be missing out if you don't follow me on both.
MathEdnet on Twitter
In October of 2009 I decided to create a second Twitter account for math, education, and math education tweets. Now fellow educators can follow me without being bombarded by tweets about the Cubs, the weather, or the latest YouTube meme.
link sharing
Delicious
I've been a Delicious user since 2002 and have bookmarked hundreds of sites. People (me included) don't seem to often use Delicious's sharing features, but for storing, tagging, and cataloging links, Delicious is hard to beat.
Google Reader
I only started sharing links with Google Reader in 2009, just in the hopes of becoming more friend-friendly with other Google users. I looked for a tool that could post to Delicious, Google Reader, Twitter, and Facebook in a single click, but couldn't find anything I liked.
personal and professional
I finally joined Facebook in May of 2009 because friends I would be moving away from seemed to enjoy it and use it effectively. I can see now why it's so popular - it works. I only friend people who are really friends in real life (or were so in past lives). I commonly post links, which I'm sure is annoying to some, but I don't spam my wall with results of cheesy quizzes and games.
One little problem with Linkedin - I haven't actually signed up with it yet. Does that make me "linkedout?"
photos and videos
Flickr
I think it was in 2005 or so when I decided I wanted a better way of posting pictures to the web. Instead of choosing Flickr, I felt I needed to host the pictures myself and used an installation of Gallery provided by my hosting provider. That was a mistake. (Gallery is a good application, but Flickr is now a better choice for me.) My Gallery installation turned out to be non-upgradeable (thanks for nothing, Powweb), but it couldn't build the community that Flickr has. Now I'm a Flickr Pro user faced with the challenge of moving 1200+ pictures from my old gallery, but having all (or most) of my pictures on Flickr will make it worthwhile. It would be a faster process if I wasn't such a perfectionist with my EXIF tagging!
YouTube
I really don't post many videos, but YouTube makes it so very easy. I only have the video camera on my cellphone, but might think about a small camcorder someday if I get more serious about the motion picture side of visual media.
music and movies
Last.fm
Last.fm might have been one of the first truly social networks I joined, even though I've never socialized on it much. It has, however, helped me find new music I've liked, and works well with Amarok, the music player in KDE.
Netflix
I might be missing something, but there seems to be no last.fm equivalent for Netflix. I have a Netflix profile but I can't seem to figure out how to post a link to it. I think you have to be one of my friends to see it. There is a Facebook Connect application, but that doesn't do me any good here, either.
aggregation
FriendFeed
In some alternate, yet similar, universe, FriendFeed has replaced both Facebook and Twitter, having trounced both. As much as I like how it works, it doesn't seem to be where the crowd is. For me, I use it as a lowly aggregator, pulling together all my postings from around the web. If you're going to only subscribe to one RSS feed to keep track of me, this would be the one.
Tumblr
I've used Tumblr as an aggregator for longer than FriendFeed, but have neglected it for quite some time. Follow at your own risk.