Where to look for last minute airfare?

[lovetoscrap]

I am trying to see if I can find a low airfare for an event I would like to attend week after next. Is there anywhere that has great airfares or would be most likely to? Neither Air Tran or SW fly to where I am going (Knoxville). I have never used any online booking sites other than just directly through the airline so not sure if one of those would help me?