There's bugbane, that's a pretty easy one to guess
cool that is also known as Black Cohosh, an ancient remedy used by menopausal women, but i think it can be used for any hormonal imbalance really.
but it grows to 8 feet tall and stinks to high heaven so maybe not such a hot idea
xp bugbanehere are some more sites i found anyway, maybe some will be helpful
http://www.virtualseeds.com/insect-main.html
http://www.ipm.iastate.edu/ipm/hortnews/1993/5-26-1993/plant.html
http://www.coopext.colostate.edu/4DMG/Pests/mosquit.htm
http://www.turtlestuff.com/insect_repellent.html
http://www.lowchensaustralia.com/health/homeremedies.htm
http://www.homeandgardensite.com/companion_planting.htm
http://www.stretcher.com/stories/980625b.cfm
well looking for those was educational, a lot of the sites mention the same plants, and some of them are plants not huge trees
sweatdrop a couple of other useful links in there too, for repelling pests from your pets and the plants in your garden(if you have one)
3nodding