Here's an article on the study on catnip vs. mosquitoes, in case you're curious:

http://www.sciencedaily.com/releases/2001/08/010828075659.htm

Deet sprays are usually 5-25% deet, so that would mean 0.5%-2.5% catnip for the same effect. I'm planning to try out 5% in two solutions -- one with sunscreen as a base for a dual-purpose cream, and one with acetone as a base for a spray. I've also heard of using coconut oil as a base.

If you really despised mosquitoes, you could use 100%, but that'd get pricey unless you crew your own catnip in bulk The pure oil is like $20 an ounce unless you buy in bulk. At the strength of a 25% deet spray, though, it only works out to 50 cents per ounce of repellant, which is affordable. Buy in bulk, and it's even cheaper.

I'll let people know how my results go when I get the oil. I'll also have to see how badly I get mobbed by cats