<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Meilensammler:
Buying a full fare first ticket will also get you into any lounge for free.</font>
This, generally speaking, is not true for domestic US flights on most airlines. The clubs are primarily membership clubs, not premium cabin clubs. Most airlines do offer this perk for trans-oceanic premium cabin passengers, and possibly for certain trans-continental flagship routes.