From an Olympus person....
Yes, the Panasonic site is a pain, things are hard to find and items "obsolete" seem to disappear from view too easily, I find that seeking information there is always a pain.
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It started with G1, a mock SLR lookalike, then later an updated G2 in similar shape. The new G3 seems to be merging the G and GF shapes into one so that may be the future. So the G line is changing.
The GH models emphasise video performance and seem to be what Panasonic regard as their top performer with the highest prices.
The G10 seems to be a one-off cheapie to get people hooked in and is same mock SLR shape as the G line. It may be a one and only model line in my guess.
The GF1 seems to be the enthusiast camera with the old rangefinder shape but no viewfinder, that was replaced by the seemingly dumber and simpler GF2 again maybe in an attempt to appeal more to the P&S converts. The new G3 may mean the end of this line already because of that shape and feature merge.
My own crystal ball suspicions are that it may eventually boil down to two product lines, the Gx to replace the earlier Gx and also the GFx (or maybe the GFx will continue in that cheaper and simpler P&S converter mode). And the other major line being the GHx line where quality video and other fancy features figure more prominently.
OK this summary is from an outside observer so Panasonic fans can jump in and fine tune my comments at any time.
If wanting to sort it out yourself then start here
http://www.dpreview.com/products/panasonic/slrs and see how the features of each model compare.
Regards........... Guy