Keep in mind that advertising a comic is a lot like advertising a lot of other things online. Treat it accordingly and start reading some blogs. Not just the ones on comics, but about running businesses, marketing, blogging (yes, there are lots of blogs on blogging -- go figure, but they're damn useful), and anything else that's associated with whatever it is you're doing. There's plenty online about running a business, and like it or not, you should treat your comic like one.
I'm trying to run my own
blog on the stuff, which admittedly is just another method of trying to advertise the comic and attract readers. That said, it still works, the information there is still useful, and you can update the blog a lot faster than you can your comic.
Find comics you already read that're similar to yours, and start making yourself known in those groups. Don't mess with DeviantArt and FurAffinity's communities (but feel free to post stuff there and try to get more exposure); they're too large, too broad, and you'll just get frustrated if you pay too much attention. Same caution applies to certain LiveJournal groups. At least with comic communities you'll have a far less jaded/dramatic crowd, and they're already receptive to the general idea of webcomics as well.
And check out Project Wonderful for later. Is interesting stuff.
