A few weeks ago I started working on an Apache Cheat Sheet - I think covers the most common configuration, let me know if you want to see anything else on there.
Looking for more cheat sheets? check out my cheat sheet roundup.
Lets face it, unless you have a photographic memory, no developer can remember all the different functions, options, tags, etc. that exist. Documentation can be cumbersome at times, thats why I like cheat sheets.