Bug Repellent

So the Roo has made me aware that she's getting bitten ad nauseum by the resident carolinian mosquitoes.
The obvious solution is to use some bug repellent, as ya'll alluded to with the Skin So Soft of Off products.
However, she's also been told that using it too much is NOT good for you. I guess any product with DEET in it, when overused, can cause some serious health issues.
Anyone ever made their own natural bug repellents using citronella oil or lemon oil, etc???? Any suggestions on what works, what doesn't work, etc?
I started to research and got to this "guide" http://chemistry.about.com/cs/howthingswork/a/aa050503a.htm