Hi Marcus! If you haven't seen it already; for promotion, we had a similar question over in the Webcomic Gubbins forum, which resulted in a pretty good list - http://www.thewebcomiclist.com/forums/viewtopic.php?t=22410&sid=854f3c594fe466a3d0d5d04c31f33513
For learning, asking questions in forums like this can be helpful - as you're more likely to get a specific answer. Also, what sort of comic are you making? You'll probably want different advice depending on whether you're writing a long-form epic or a gag-a-day strip. I write long-form, so I tend to know more places for that type of thing.