A few that I didn't see listed that I enjoyed quite a bit;

The Guardians of the Flame series by Joel Rosenberg
-Basically a gamers dream. Playing in a table top rpg and then waking up to find yourself as your character in the game. Rather large series that is still being added too.

The Keepers of the Hidden Ways series by Joel Rosenberg
-A very norse feel and approach to gods and communities. Very well written fight scenes and interesting twists in the story.

The Last Rune series by Mark Anthony
-Jumping between dimensions of modern day earth and a fantasy world where magic is around. Problems come when people start crossing into each. I believe this one is six books in all.

Just a few series I would suggest. I can't suggest just one or two books, they all are well written IMHO.