Post em' if you know em'!
Here are a few that I know of:

Lackadaisy: An incredibly well done comic that, to my surprise, keeps improving. It updates infrequently, but is otherwise very good.

Las Lindas: What started as a rather interesting comic about actions and their social consequence soon turned into a bland mini-drama with no real jokes. It's worth a read, but once you see the alien spaceship, it might be a good idea to stop reading. It has sexual references and contains questionable content; I'd recommend younger members to stay away.

Two Kinds: It starts out rather horribly, but slowly improves, and I mean sloooooooooooooooooowly. The humble beginnings of bad writing and worse art slowly turned into a rather interesting read, with the current story arc being, in my opinion, the best one thus far. While featuring no actual lewd content, the story often makes reference to it and the lead female often appears without clothing.

I know that two of these are more TV-14 than PG-13, but to be honest, that's actually pretty tame.