There are all kinds of standard review sites out there, like CitySearch and Yelp, but it can be tough to suss out the worthwhile haunts. Here are a few other sites that do things a little differently:
This is Beer Advocate's geographically-based guide to beer-centric establishments. The beauty of BeerFly lies not in its user reviews and careful scoring system but in its strict listing requirements. To be included in BeerFly, ya gotta be beer related. That means you'll find brewpubs, beer bars, beer stores, breweries, and brewing supply shops. This rules out a lot, though, so you better be ready to drink beer.
Chowhound is a gourmand's wet dream: with city-specific discussion boards and topical boards as well, users can find answers to almost any need. And although the focus is food, you'll discover that food lovers are often booze lovers, too.
This is a brand new site that looks promising: it's simply a map-based locator of every bar, club and liquor store located in any of 19 different US cities. Users can search by zip code, add locations and leave reviews or comments in the currently quiet discussion forum. With no major plans for additional content, the site is no-nonsense: it's basically an online phone book for the boozehound.
In addition to the above resources, there are other ways to uncover the best kept secret in town. Try chatting up your favorite bartender to discover where s/he drinks (please don't be a creepy stalker about this, though). Keep your eyes peeled when wandering around new neighborhoods and don't be afraid to stop in and have a quick pint to suss a place out. And above all, maintain an open mind and a willing liver.