OneLook Dictionary Search is a search engine specialized for searching dictionaries ("6,067,605 words in 963 dictionaries indexed"). They've got a cool reverse dictionary too: search for "causing anxiety" (I've always wanted an adjective to describe things that cause anxiety) returns:
anxious weighty troublesome tense worrisome serious grievous dangerous uneasy severe grave distressful distressing heavy unquiet worrying disturbing nervous perturbing troubling care sweat distress fear alarm
plus hundreds more. The search is noisy, since it is by its nature fuzzy, but still useful. Also, you can use wildcard characters so it's a great way to cheat at crossword puzzles.