Zipcar alternatives?

I'm a little hung up on their $75 activation cost ($25 one time fee and $50 annual fee). Especially since in the 11.5 months I've been in DC this is only the 2nd time I could really use a car (not just being a very nice convience).
I haven't really been able to find anything on the net. I'm think I might go the rental car route, which would cost about $30 for the trip itself, but would be about $40 cheaper for this trip because there are no annual fees or activation costs.
Does anyone have any suggestions?

...
http://www.zipcar.com/dc/check-rates
$25 activation, $50 annual, plus probably 3 or 4 hours for another $27+, so at least $102 if not more, rental car would mean maybe ~$70/80.
Its frustrating to pay that much for an annual membership when I don't need to drive more than once or twice a year... Argh!
I'm still thinking about it because the plus is that if I need a car anytime in the next year then its only the hourly rate...

Ah
It looks like they have increased the annual fee, because I am only paying $25/year. But yeah, if you plan on ever using a zipcar again, then it is probably worth it to start a membership for your 3-4 hour trip.
One of the really great things about zipcar is that they have excellent customer service. They have always been really nice to me whenever I've needed something or had a problem.
Couple things
The zip car membership I'm on only costs $25/year for membership (the one-time $25 app fee was waived because of a collaboration between zipcar and my school), so I think you are wrong with the $50/year part. Maybe you are getting confused with one of the other membership options which require you to committ $50/month to driving?
If you are taking a day trip or vacation where you drive long distances, then a zip car is not for you. With a zip car rental, you get free gas, free insurance, but only get 125 free miles per day (after that you pay like 40 cents a mile).
So if you are making a road trip, rent a car. If you want to drive around town, you can't beat a zipcar. Especially since most rental cars charge you like $20/day for their insurance.