What vintage/modern flashes are compatible with the Canon A-1? I'm going away for vacation and I need something other than a tripod for low-light situations.
Everything with a standard hotshoe should work. Flashes are pretty universal, even today, you can buy a Nikon flash and use it on a Canon camera all day long.
The flash should support a manual mode though. The A-1 doesn't have TTL (what is used to sent data about exposure to the flash, telling it how powerful the flash should be).