Thanks hinting and Godfrey. I'll definitely look into the Olympus FL-36 and 36R. What are the differences between the two?
The FL-36 is the older flash, and the FL-36R replaced it. You won't be able to use the main new feature of the FL-36R (remote flash TTL support) on the G-1, since Panasonic doesn't support that (only the E-PL1 of the micro 4/3rds cameras supports it). The FL-36R can act as a dumb slave if you want to get into strobist type setups (the FL-36 needs a trigger to act as a dumb slave).
I put together a list of flashes that support Olympus (and Panasonic):
http://www.the-meissners.org/olympus-flash2.html
Personally, I tend to think the heavier flashes (FL-50, Metz 50/58) overwhelm the micro 43/rds cameras unless you put the flashes in brackets (and by the time you get to a bracket, the camera is no longer micro).
Also, does anyone have experience with the Vivitar DF383 or Nissin Di 466? They seem like decent, cheaper options.
The main thing that you loose is FP-TTL mode, which is useful if you are trying to use the flash as fill flash on bright sunny days, or when you are using a fast lens like the 20mm wide open. FP-TTL mode allows you to get a faster shutter speed than the normal flash sync.
Note, Vivitar has two other models (183, 283). If you go for the 283, be careful, since the Vivitar company sold the flash unit to Sekur and they reused the model number 283. The original 283 was a generic flash used by generations of photographers, but it tended to put hundreds of volts through the hot-shoe, and would likely fry your camera. The new 283 is dedicated to a given camera (in this case Olympus/Panasonci), but you get a few more features by stepping up to the 383.
The Nissan does not swivel, which means that you can't use the flash other than firing straight ahead (i.e. ceiling bounces) when the camera is in portrait orientation. You can do a ceiling bounce when shooting in landscape orientation and crop the photo to portrait format. On the other hand, the Nissan has a faster quoted recharge time (4 seconds) than either the FL-36R (8 seconds) or Vivitar 383 (9 seconds).