Friend of the VRT, Caleb Jaren, recently showed me some cool work he's done creating a Snort "User Defined Language" in Notepad++. This UDL provides flexible syntax highlighting, rule validation, and general assistance as you're getting familiar with the Snort rules language and its capabilities. It's freely available on his site, and he's looking for feedback and testing from the community.
Thanks, Caleb, for the great contribution to the community. Windows users, have fun with this useful new bit of code!