There's a lot of good webcomic tracking sites/services out there but today I want to flag the one I've been using this summer to catch up on many series I had slipped on reading.
It's called Piperka and it's pretty handy. Create an account there and check off the comics you want to watch and it tells you how many episodes of the comic you haven't read yet (you can tell it to start at the begining or end of the archives when you start). As comics update you see that you have more to read. If you're reading the archives you can tell the site where you stopped so you can pick up where you left off.
It doesn't have every webcomic listed of course, but anyone can submit a comic to it. (It will only take webcomics that have fully accessible archives though). It only takes a few seconds to submit something so go do it! (that way I don't have to submit as many of your webcomics myself!…)