I've been doing taekwondo for about nine years now. It's good fun, and pretty useful for keeping fit. Might not be the best martial art in terms of actual self defence, but there are definitely techniques I've learned from it that would apply to a fight in the street. Plus my instructor is really good and often takes us through self defence techniques outside of tkd.
I actually went to a few competitions when I was younger, until one fight where I got kicked in the head and was pulled out by the medics because I looked concussed. Haven't really taken part in many comps since then :P
One of the guys at my club does aikido, and every now and then he'll bring along a couple of swords and some of us train with him. It's good fun, and I'd like to start training at it properly, so I suggest you should definitely give it a try.