If you really wanna get the RoC/TFT campaign maps, you have to use a MPQ-editor (there're some in the tools section). Then open the war3.mpq/war3x.mpq, search the maps and extract them.
EDIT: hey wait just a minute! 1) The RoC and TFT campaigns have to be in war3 files; i mean, isnt there a way to open the maps without having to download MPQ?
1) The WC3 mpq-files contain all the data used for the game (models, skins, maps, ...). So, if you wanna have them you need to extract them, dunno if there's any other way. 2) I suggest WinMPQ, here's a quick-link (only working for Win2000/WinXP) http://www.wc3sear.ch/index.php?p=Tools&ID=1&sid=22dd6ee13f479936143808ffea17048b