After each show Gary Hoey and his band hang out and just chat with anybody willing to stay. I talked guitars with him for about 20 minutes after his Ho Ho Hoey show here in San Diego last year. Definitely the coolest 'famous' musician I've met.
Met and chatted very briefly with Alex Lifeson on the Signals (maybe Grace Under Pressure) tour at a meet and greet.
I saw Eric Johnson on the Ah Via Musicom tour at The Varsity near LSU. Student discount price? $8! One of the best shows I've ever seen. Played everything very close to the album, but added alot more to each song too. Very cool to chat with, and as Cagey says, very professional.
There's a local guitar shop that has meet and greets with many of the big names that come through town. I saw Satch there once.