These are 4 websites I've discovered that have helped and are still helping me map.
I prefer Gamewag over them all..
Check them out, I hope they help you too.
EDIT
Some Gamewag links don't work now. Sadly..**
1) Gamewag
http://gamewag.com/hl2.html
2) Chatbear
http://www.chatbear.com/unity2/4989/600,1119639957,1163/871881?v=flatold
3) Turorial Hero
http://www.tutorialhero.com/view-584-valve_editor_tutorials.php
4) Valvesoftware Developer
http://developer.valvesoftware.com/wiki/Source_SDK_Release_Notes