I've a big fan of Jeph Jacques, specifically Questionable Content and Alice Grove. Both contain mature language and some NSFW images though, be warned! Both have an ongoing plot (QC's goes back YEARS) so be warned if you try and dive in. Alice Grove is very sci-fi though, has a neat mystery woven in and started maybe only a year ago or so, so very doable in terms of catching up.
Besides that XKCD is good fun, and Dinosaur Comics is done by a local, so I'm biased for that one! Neither have ongoing plots so easy to dive in.