Some nifty but obscure (obscure to relative Unix newbies like me anyway) things come along with the BSD layer. For instance there's the "look" command, which by default searches /usr/share/dict/words (a list of about 250,000 English words and proper names). You can't use regular expressions with "look", though. For more flexibility (let's say you're a word-game nut), define this alias:

alias words cat /usr/share/dict/words | egrep

To mimic the behavior of look foo you'd type words -i ^foo, but now you can do many more cool and useless things (like finding all words in which the letters "abcde" appear in sequence: words "a.*b.*c.*d.*e"). You'll be completing impossible rhyming couplets faster than you can say "zygosporange."