A good, decently-priced prebiotic supplement is inulin by NOW. I've taken it in the past, but didn't stick with it long enough to see if it did anything for me. It did seem to cause me some gas, so make sure to add it in slowly. Probiotics can cause an increase of gas at first, too, (they didn't for me though) but this should go away in a week or two. Some dietary sources of prebiotics include soybeans, Jerusalem artichokes (which contain inulin), jicama (also containing inulin), chicory root (inulin source), raw oats, unrefined wheat, and unrefined barley. FOS is a prebiotic that is often added to foods.
I take the same probiotic as pb4. I've also used Ultimate Flora probiotics, which were good, but they were more expensive. I buy most of my probiotics and prebiotic supplements at iherb.com. They have pretty good deals. Probiotics are also in yogurt, kombucha and kefir. I would suggest yogurt brands like Stonyfield Farms and Brown Cow. They have more strains of bacteria in them and less added preservatives (if any) and sugar.
Just noticed that Wikipedia has a really good break-down of areas in which different probiotic strains are helpful (not sure how accurate it is, since it's wikipedia, but it looks pretty good): http://en.wikipedia.org/wiki/Probiotic
Sorry to hear you were diagnosed and had to go to the hospital.