This doesn't entirely match the criteria in your question but I think dipping into the standard library for your language (if it has one) is a good idea. It's n

This doesn't entirely match the criteria in your question but I think dipping into the standard library for your language (if it has one) is a good idea. It's not only useful to see what you're using but it can also show you how language experts use the language (which can be useful stylistically) and be an archaelogical exercise in the history of the language and its priorities (particularly true with Ruby's stdlib, I found).