Most all of the good ones are either skyventure or ifly. There is A LOT of difference in tunnel generations. Essentially there are 3 generations so far. If you find an old 1st gen (Pigeon Forge, TN comes to mind) don't waste your time or money. That generation was woefully underpowered and required really big "balloon suits" to lift you and the column of air does not extend to the walls of the chamber. 2nd gen (iFly Orlando) is much better but still has a limit for advanced bodyflight such as sit flying and head down because they can not generate the wind speeds needed for those disciplines well. 3rd generation tunnels have the air recirculated (NH is one of those) and can handle the speeds for all orientations for bodyflight.
Most people (read non skydivers or inexperienced tunnel flyers) just do the normal tourist type flights where they pay say $60-$80 depending on location, etc. for 2-4 min total flight time. Have a tunnel instructor hold on to them and help them kinda fly in the tunnel. Like someone said they usually hold on to you the whole time. For experienced people we rent the tunnel in block increments from as little as 5 min to hours. I usually rent for a hour with friends and share the time working on different things. Once you are used to it you can fly for long periods of time but as someone said, early on flying in a tunnel you will be sore for flying more than a few min. The rates are dependent on the generation and diameter of the tunnel. Raeford, NC is the biggest in the US at 16.5' and if I remember correctly an hour is a little over 1100/hr for rental in block time. orlando is around $750/hr.
Btw if ya'll have not figured it out yet, I am a pilot and also a skydiving instructor (Accelerated Free Fall Inst and Tandem Instructor). I have about 10 hours of tunnel time mainly at Raeford, Orlando, and Denver.
Hope this helps fill in some info.
Andy