While xkcd and Cyanide are self-contained strips, other webcomics have taken taken the route of epic fantasy - literally. My favorite example of such serialized goodness is The Order of the Stick - a.k.a. OOTS.
The Order of the Stick, follows the adventures of a team of warriors who are battling the great evil of Xykon. And while they are on this quest, they are constantly fighting monsters, dealing with silly detours, gaining XP points, leveling up all while making wise-cracks about the nature of role playing games (Dungeons & Dragons in particular).
If you like role playing games (RPG), you probably have already heard of this comic. Even if you have not heard of RPGs, the comic more than stands for itself beyond the arcane lingo of skills, checks and levels. Ignore it, and in no time you will start to realize what those terms really mean.
At the time of writing this, there are a total of 743 episodes available. Everything you need for hours of role-playing, comic fun.