Drylok Masonry Waterproofer. The Home Centers, Hardware Stores, and Lumber Yards carry it. There's latex-based product too. DO read the label before you leave the store. That way, if you have any questions, you can ask while you're there.
If you have seeping water, that's another issue. If it's mainly condensation, the Waterproofer should be fine. Go to UGL Masonry Products for more info.