I use Thunderbird nowadays. It's my main web center. Used to be iGoogle, which is still my homepage, but I get all my mail and all my RSS and most of my news and my calendar through Thunderbird, so it's almost useless for me to have a homepage now. Keeping up with email and RSS counts for the majority of my time, and it's great to know that I can keep updated without effort just by being sure that everything delivered through Thunderbird is read. No more refreshing or random stumbling upon sites. I also removed all RSS feeds from LiveJournal - so my friends page is actually my friends page again.
Facebook is my main social networking site - where I try to keep all my real-world social information up-to-date.
Jaiku shows my activity online, but I'm quite taken with FriendFeed as it's always more up-to-date. But seeing as Jaiku was just bought by Google, it looks like I'll stick with that as my primary place to get updates on what I've been doing online - then again it's not like it takes any effort to keep both up to date. That's sort of the point of the sites.
As for my activity online, there's a number of things:
Twitter is my micro-blogging site of choice, even though Jaiku offers it too. Twitter is the O.G. of micro, though, and has the largest user-base and ease-of-use. If you're only keeping up with my LJ, you're only hearing half the story!!! Only not really.
A lot of people seem to use del.icio.us as some sort of linkblog, but I joined it a while ago to just use it as a live bookmark site. It's a lot easier to save my bookmarks on the site and be able to access them on any computer, rather than toting a bookmarks file around and installing it on every browser I use.
I don't know if it's even worth mentioning that I use YouTube. I don't have an account on any other video sites, though, and I used to put vlogs on YouTube, as you can see.
Flickr is my main photo site - I just dump everything I can find, minus my daily photos, to Flickr. Facebook's got a nice photo interface but it has limits on album size and photo dimensions, so it's good for things specific to communities. Therefore I don't use it as often.
I use Last.fm to keep track of what I listen to, and more recently I've switched to it for hosting my music. Great that it kills two birds (of a feather) with one stone.
That's about the entirety of what I do online. Don't know if you've noticed, but I haven't linked to my own site once until now. That's the beauty of the current era of the Internet - the need for a personal site is completely nil. Might as well hop on a social networking site to share your stuff around - that's what I do. My site's just there to act as a portal to sites relevant to my online presence - and I also use it as a host for random stuff.
I wish my iPhone added to the simplicity of the whole thing, but it's not as great with all this stuff as one would imagine. I get my email fine, but what about my RSS? The only RSS reader is an online HTML-based one, which doesn't update often. And seeing as my bookmarks are RSS - it's very difficult to access Twitter, just for example. Also there's no Flickr interoperability. And the calendar is useless to me since it won't sync with anything on Windows except for Outlook/Express, neither of which I have. Oh well, maybe Apple will eventually get on the ball.
I'm always on the look out for other stuff to keep updated with, or stuff that'll simplify my online activity. I've looked at Plaxo which tries to act as a sync service that blends all of my services into one. It does a pretty good job of it, but I still don't get too much use out of it. I might start using Tumblr as a place to do a linkblog like Awesomelinks, but so many things I use already offer similar services - del.icio.us, Facebook, Digg, etc.
Well this was a good use of an hour, I'm going to bed because I'm not feeling too hot. Goodbye!