For my weekly D&D sessions, I picked up an irregular Chessex Mega Mat (I also aquired a Mondo Mat recently). It's vinyl, has 1 inch square grid on one side and hex on the other. You use wet-erase markers on it (available at OfficeDepot in a rainbow of colors quite cheap) to draw out your map and then use paper towel with water to clean it up. This could be easily incorporated into a framed table.
Check out
Chessex Factory Seconds for more info. Local gaming shops also carry the Chessex mats, it's where I got mine.
-G