Some LGBT establishments in Las Vegas are listed here.
http://www.vegas.com/nightlife/gayclubs/
I have been to Vegas a number of times and greatly prefer mainstream. There is nothing special or unique about the gay bars and clubs in Vegas compared to those in any decent sized city. Drink and Drag is the most interesting one, and I agree with the previous assessments. Most gay bars and clubs are well away from the Strip, thus not convenient if you are staying on the Strip. I had way more fun in the mainstream places including multiple casinos, restaurants, bars and shows.
Search this forum for Diva Las Vegas and you will find posts about Vegas experiences.