Ex Officio's BUZZ OFF apparel is an effective weapon for mosquito self-defense. The Wicknit hooded sweatshirt is a nice little combo piece that not only wicks moisture effectively, but is treated with an "insect shield" that helps repel bugs and lasts for up to 30 washes. The hood is a nice touch, and it fits snugly for extra protection.
It's no more foolproof than any other means, but in my unfortunately extensive experience with nasty Alaskan mosquitos the BUZZ OFF treatment appears to cut down on bites. The shirt has a kangeroo pocket in front, a zippered security pocket inside and long sleeves with thumbholes. Nice for moving through mozzie country, and packs down small for travel.