I need to rent a car this weekend to go to Atlanta. I need car insurance on the rental, but don't have car insurance. I don't want to pay $90+ a day in full coverage. Does anyone know if Geico or any of the major insurance companies offer rental insurance. Since the mark up is so high on rental insurance from the rental place, I figured they'd offer rental insurance at a more reasonable rate.

Anyone have any ideas how to save money on rental insurance, my CC doesn't cover rentals. I'd use the car 3 days, but can't really justify spending literally a one way ticket across the country to do it.

90$ / day sounds very high, I'm used to ~$20-$25/ day... I'm in Canada, so maybe that explains it.
IIRC there are 3 kinds of insurance offered.
You likely really only need the damage waiver and not theft and the other one ( sorry I'm tired and don't recall).
Good question about getting separate insurance from the agency though; I would like to know if that's offered.

Normally insurance agencies only offer insurance on a rental IF you were given a rental because your car is in the shop. I don't know if they give it to you on a case basis for renting.

If I have to get insurance on a rental, I get the loss and damage waiver. On average it is $12 a day and then you can beat the hell out of the car. Take it off-roading, throw rocks at the windshield, get into a gunfight during a high speed chase. It's all good! I'm exaggerating but if you get a ding or a rock hits your windshield or you get some other normal damage, or the car is stolen, you don't have to pay for anything. I had a rental company in Austria try to charge me for paint transfer on the side view mirror but thanks to having the waiver, the $250 they wanted never saw my pocketbook. Another time I rented a car in Chicago and went to Canada and blew a tire there. Not wanting to drive all the way back on a donut, I called them and thanks to the waiver, they had another car sent out to me. Of course it was fun to think someone in Chicago would have to rent a car that had km/hr on the speedometer rather than mph...

v6,
boNes

What Bones said. The extra $12-17 a day is great in case someone dings your car in a parking lot. I had a buddy hang his rental up on a guardrail once. The new rental car showed up while the wrecker was getting the old one off the rail. He signed the paperwork and drove off. No charge.