Most of my collection is boxed up right now, but like spades1013, I've been playing a long time (1977), and actively collecting older stuff since I learned that Dragon sold back issues way back when.
My shelves are somewhat thinned out, and better organized now, but these pics from 2008, 2009, and June of 2010 give a good sense of about 60% of my collection: they don't picture many of my miniatures sets, or the stuff that's boxed up in the attic (magazine collections of Dragon, Polyhedron, Dungeon, White Wolf, Different Worlds; additional wargames; etc.)
So, without further ado, here are the older and more current pics (newer toward the end):
This pic (above) is to show off my wife's "dust guard/make the gaming stuff look less ugly in our bedroom" tapestries; there's one on each of the two 48"x80" bookshelves in the room.
My modern rpgs shelf (same one picture above, just with the tapestry rod removed, which is what I usually need to do while looking for a title). This includes my Call of Cthulhu, Ars Magica, RuneQuest, Star Wars, 3.5/d20 stuff (mostly WotC and NG), Fading Suns, and White Wolf Storyteller stuff (mostly 1e WW, some 2e I suppose).
This is the opposite wall of the room, to help share the awesome disarray of my stuff

---some of which is caused by the various baby boxes in front of the gaming stuff in front of the fireplace (the picture is sitting on the fireplace lintel), but I just haven't made the time to get it as organized as I need to yet. I do have another week of paternity leave coming up, though, so I'm hoping to make some good headway then.
The above two are some of the boxes in front of the fireplace, and the table between the fireplace and the other bookshelf.
These two are the bookshelf at the right-hand side of our bed (my side). This is where some of the non-TSR D&D is (top shelf), most of the rarer non-TSR stuff, my AD&D stuff, and the Greyhawk campaigning binders, RJK/EGG correspondence/manuscripts/etc.
These are views into our turret room, which is on the front of our house, and off of our bedroom; we'd originally envisioned this room being a baby nursery, but it's been storage since we moved in. There are 4 standard-sized bookshelves along the right wall, and lots of boxes piled around in front. Many TSR boardgames and other misc. boardgames I don't want in the kids' reach in the basement are here too. The shelf closest to the window has gaming magazines, the next shelf has one shelf of overflow magazines, and three shelves of my HPL and related fiction (the rest of my regular fiction bookshelves are also in the basement); the next shelf is Moorcock stuff; the final shelf was supposed to be Neil Gaiman stuff, but got taken over by various and sundry medicines, shampoos, tissues, and other extended-bathroom supply stuff since our bedroom bathroom is pretty small and has essentially zero storage. So, the Gaiman books are boxed up on the floor, along with all of my miniatures, a few boxes of AH/misc. wargames, and some other bric-a-brac.
These last three pics are the HPL and MM shelves.
My collection is making good progress: I've spent several weekends organizing, sorting, and such, and am nearly done with that stage of things! If you scroll back earlier in the thread, you'll see the mess that our bedroom and my storage closet were; things have definitely improved, in the bedroom in particular, where most of the extra boxes have been organized, consolidated, grouped, packed up, labelled, and migrated to the attic:
The boxes remaining in front of the fireplace are AD&D hardcovers and modules (still need to be sorted and grouped beyond shrink/non-shrink), as well as the more-valuable non-manuscript items like OCEs and supplements, Tractics sets, quarto-sized non-TSRs, and wargaming magazines.
Both of the big bookcases are now focused on my immediate research and writing needs (i.e., Greyhawk, dungeon design, Gygax, Kuntz, etc.), and the other rpgs I'm most-likely to play besides D&D in the near term (Call of Cthulhu, Ars Magica, Paranoia, etc.). Both have some open space that I'm still in process of re-sorting to a more-optimal configuration, and I still need to spend more time with the CoC materials to better organize them too.
The closet room is also much-improved, though still a bit of a mess, which is mostly caused by my boxes of minis that aren't as nicely organized as I'd like, and the Moorcock and Gaimon books that I boxed up to make room for shelving/sorting space. The closet will improve once I start to cull the duplicates and unwanteds in earnest!:
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One more weekend of work, and I think I'll be good-to-go!
This last image is the main board/war games shelf in the basement, although some of this has also been packed up more recently, too.