One of the interesting things (although not entirely unexpected) to happen in the wake of the release of Dungeons & Dragons Fourth Edition was that Third Edition didn't actually die. Yeah, the fact that all of the rules were released as Open Content with a license that doesn't expire and can't be revoked means that people who weren't all that interested in the new rules can continue playing the old rules, and most importantly (because they always could do that in the past too) they can continue to have support from third party publishers who create compatible material for their 3.5 games!
One of the prime purveyors of 3.5 material has been Paizo Publishing, the former publishers of Dragon and Dungeon magazines. Their bread and butter has been the Adventure Path modules; six fairly long, interlinked modules that are designed to take a character from 1st to about 15th or so level in a grand story arc. The adventures also come with a lot of other material; setting material, several new monsters, etc. and are a pretty good buy for the money, in my opinion. And I say this even as a guy who rarely (if ever) uses adventures "right out of the box." I've still found plenty of material raid-worthy. Not only that, the setting that's gradually been revealed is very interesting to me. It's got just the right about of references to old pulp and swashbuckling adventure stories, plus just enough new and exciting innovations; just enough tried and true D&Disms and just enough new directions and vistas.
Granted, I'm still going to raid it for inclusion into my own work (mostly) rather than attempt to run anything in the setting as written, but I've got to say that the Pathfinder setting has really won me over. In fact, I think I reviewed it here several months ago and said as much there.
So, in an example of fanboyism, I'm going to list the currently available and upcoming products from the Pathfinder Chronicles and Pathfinder Companion lines that I'm interesting in buying but have not yet done so. I do have a fair amount of the currently available products from both lines already, and I'm not listing those. These are all setting books of moderate length. Actually, the Companion books are fairly small.
Into the Darklands
Dark Markets - A Guide to Katapesh
The Great Beyond - A Guide to the Multiverse
Princes of Darkness - Book of the Damned Vol. 1
Cities of Golarion
Guide to the River Kingdoms
Taldor - Echoes of Glory
Qadira, Gateway to the East
Cheliax, Empire of Devils