I've had my G11 for about 6 months now and would really like to look into getting some new lenses(really wanting a macro lens) and possibly some filters. Anyone with this camera(or similar) have recommendations on what lenses will work for this camera(do any of the lenses work or do I need smaller ones??) or what filters/what do I need to do to use a filter with it? Thanks in advance as I"m fairly clueless about this stuff. I've gotten pretty good with the stock lens and would like to move into other lenses now as well.
Hmmm, I'm not sure that the Canon G11 actually accepts interchangeable lenses.

The lens on the Canon G11 is permanently attached to the camera body. I'm not sure that G11 users are able to remove the lens and place a new one on. (I had a Canon G10, and I wasn't able to remove the lens)
However, you
can attach adapter lenses on top of your current lens. This is not like dSLR cameras, where you remove the existing lens and replace it with a different lens. Instead, placing an adapter lens is like placing glasses in front of your current lens.
On page 163 of your User's Manual (
link), Canon offers a
tele-converter (TC-DC58D) that you can attach onto your lens. This teleconverter will change the focal length of your lens by a factor of 1.4x (ie. instead of zooming from 6mm - 30.5mm, your camera with the teleconverter will zoom from 8.5mm - ~43mm).
Also, to use this teleconverter, you also have to purchase a separate
Conversion Lens Adapter (LA-DC58K). This Conversion Lens Adapter gets attached onto your camera (as described on p. 163 of your manual). Afterwards, you attach the teleconverter onto this Conversion Lens Adapter.
The only thing about placing a lens-in-front-of-a-lens, like you'd be doing with this teleconverter, is that you run the risk of possibly affecting the image quality. You're probably ok if you stick with Canon products, but you never know with no-name brand teleconverters. You'll have to look around the Internet to see what other people's experiences are with a teleconverter on their G11s.
I believe that the teleconverter is the only lens offered by Canon for your G11. There are 3rd party lenses made by other, non-brand-name companies that may also fit onto your G11 + Conversion Lens Adapter. You might look on
Amazon or eBay. If you look hard enough, you can find a "wide angle, fish eye" lens, a "3x super telephoto lens", and a "0.43x super wide angle lens" for your Canon G11...all made by unknown companies.
For macro photography, looks like your G11 already has a "Macro" setting (see page 77 of your manual). With macro photography on the G11, you can already place the camera to within 1 cm (0.4 inches) of your subject. I'm not sure there's any additional "macro lenses" that you can place on your lens that will get you any closer than that.
Anyway, the Canon G11 isn't actually meant to change lenses, like for dSLRs. However, "technically" you can add additional lenses onto your current lens. Again, I believe Canon only offers 1 lens for your camera. All other lenses for the G11 are made by third-parties.
Hope that helps.