Bing Weather is well worth the free download for its pretty, dead-simple design and comprehensive weather reports.
With its unique features for both hotel and flight search, Hipmunk is unquestionably one of the best travel apps on the market.
If you want to send full-size snail mail postcards with your own photos, Postcardly Postcards makes it incredibly easy and convenient on your iPhone at an affordable price.
While Minutely's crowdsourced weather data is certainly a brilliant idea, it still needs an updated interface and more users to be considered a go-to source for weather information.
For now, Field Trip is probably best viewed as a fun and interesting novelty, not a local-search necessity.