Ask YC: How to determine whether or not you should list a particular technology on your resume?

Pretty much every job posting I see lists a bunch of "required" or "desired" or "preferred" technologies. Sometimes I've heard of them all, sometimes I haven't. However, I've never encountered a list where I feel I can truthfully claim significant experience with everything on it. Do you apply anyway? Additionally, how would you determine whether or not you are comfortable enough with a technology to list it on your resume, or apply to a job with that language in the title? For example, I've started learning python to build a db-driven website. But, just because I have something that works doesn't mean I now consider myself a python hacker... or should I?