I actually had to introduce my boyfriend to my parents and I had to introduce myself his parents last Saturday. If he's a nice guy - there should be nothing to be nervous about. =) It was my first time doing it and I can honestly say it turned out great! Just be brave and be proud that you have a good guy.
I'm single and proud (lol), but I would be completely freaked out if I had to. Just take a few deep breaths, concentrate on what your going to say, talk about it with your boyfriend before he meets them, and do not, I repeat DO NOT, overreact to what they say.
I generally avoid that step altogether with girlfriends. There is a chance that we will break up, and meeting my parents would therefore be unnecessary. Until marriage is genuinely on the table, meeting the parents isn't generally a good idea.