Useful resources for learning and using hammer

Valve developer wiki basically everything you need to know for source mapping and modding in general.

Nem's tools a collection of tools for source mapping and modding

3kliksphilip's tutorials a bunch of short tutorials for the more basic parts of using hammer, these really helped me when i was first starting

TopHATTwaffle's tutorials more in depth and advanced tutorials

Hammer++ A better version of hammer, would highly reccomend if you want to keep your sanity