@ Bubzilla,
i have a Inon D-2000 on my G11 with Patima housing and it work more than fine.
Every optical slave strobe will work on the G11, some easier some are more complicated to handle.
Cheap and maybe weak strobes are:
INTOVA ISS 2000
BONICA Neon Head
LYMPUS UWL-1 (Olympus says that it's especially for the Olymous cameras, i doubt that, but you never no...)
IKELITE AF-35 or DS-51
Epoque ES-150 DS
Medium priced and maybe more powerful strobes are:
INON S-2000 / D-2000 / Z-240
SEA&SEA YS-110 alpha
You may check this article too: http://www.digitaldiver.net/strobes.php
@deucebrennan
for real, true and even illuminated wide angle shots you need at least 2 very powerful strobes like the S&S YS-250 pro, Ikelite DS-200 or the INON Z-240.
Often you get much better pictures shooting with ambient light. Shooting JPG needs a manual white balance bevore every shot while
pictures recorded in RAW can have the white balance done while editing the pictures.
Some interesting pictures can be taken using the strobe to illuminate and isolate the foreground while the middle and background is illuminated
by the ambient light. This requires often a manual exposure to override the cameras brain and will to expose "everything" right,
where often the camera is wrong because she exposes perfect the forground but the background is too dark or the reverse.
Chris