Is there a place that gives a quick lowdown on every character’s strengths and weaknesses, so I can learn each character a bit and find out what seems like a good one?
I recommend looking at the stickies in each of the individual SSFIV character sub-forums. But if you’re in a hurry, you can probably just read the front-matter on each of the SSFIV character pages at eventhubs.
If there were a short summary you could read in one sitting, I doubt it would be very useful.
-edit- Yeah, iplaywinner.com is probably the most succinct of the three.