Day of Defeat Source is a fantastic game that if it had more official maps would be perfect.
The official maps for this game are quite fun indeed, them being: anzio,kalt,argentan,jagd,colmar,avalanche,donner,flash. they all give a wonderful sense of urban combat. The community is great, but it is falling verrrry slowly :'(. You will also find LOTS of custom maps, the greatest in my opinion are Orange Fight Arena and 4 Towers. The classes in this game are fun to, those being: rifleman,assault,support,sniper,machinegunner, and rocket. However steam can be a letdown at times, sometimes the friends list wont work, sometimes your favourites will disappear, but the good things about steam are: free weekends, disc isnt required for everytime you play, and when the friends list is working you can join your friends game directly through there.
I STRONGLY reccommend you buy this game!