Regularly - mu-43.com and seriouscompacts.com...but recently due to purchasing my Leica X1 I also read and post a bit on L.Camera Forum. That's it for regular forums. If I'm researching something I go to many sources. GetDPI seems like a very helpful place....but I've never registered. I'm afraid if I did, I'd never be offline.
I am still subscribed to several forums but I am only in very few active. Until recently I were active in a Nikon forum, but since I don't own any Nikon anymore, I quit participating there (although it is a great forum). At the moment I am only active in Mu-43.com and SeriousCompacts.com.
GetDpi is a too much "Fun" place for me .... they seem to have "Fun" with everything .... (browse their posts to see what I'm talking about) Also when a new camera comes out all the regulars buy all the appropriate adapters and lenses, "have fun" talking about them and subsequently dishing them for the latest greatest... and the whole thing starts again ..... maybe nice for technologists but not so much for folk interested in pure photography as in the final Image, I actually haven't seen an interesting photographic result yet on the appropriate forum on GetDpi. I like to read TOP, not so much a forum but a very interesting site for photography in general, in the meantime I'm out with my X1 to have some "FUN"
Dpreview, mu-43, and seriouscompacts. Have not posted at dpreview in a long time, as I have found many of the folks on the camera forums are very contentious. However, I was able to find great help for certain printing issues I had in the Printing and Mac fora.
I only post on this forum and blipfoto (which is not really a forum but more a combination PAD and blog). I check out DPreview,TOP, the Leica forum and Luminous Landscape reasonably regularly and post very occasionally on the Leica forum.
My first forum was Digi-Darkroom and I still visit there daily. I was also active on Four Thirds Photo and Four Thirds User but no longer visit (since moving to micro 4/3). Posted on DPR for a while but like many moved on.
I recently joined this forum because I own a Olympus E-P1 have an Leica X1 on order so joined the Leica Users Forum to learn the the pros and cons first.
I also have been a member of Flickr.co for some years.
I think this is one of the best ways to learn about both the camera(s) I own and get general hints to hopefully improve my photography.