I've stopped at Safeway for tickets before and unless you have a 'Colorado Pass' there was no discount for buying the lift ticket there. Sometimes small ski shops will carry them for $5 off, but they're really hit or miss. The best thing I've found for discount tickets is to order ahead. If you're like me you don't know where you'll ski until you get the morning snow report.
I've bought and sold 'used' tickets at the base and never had a problem with it. Signs say that you can't scalp but I've had the ticket counter verify a scalped ticket before w/o hassle. I once bought a 3 day pass off a guy who's wife got hurt for $45!
If you're in the Denver area I would hit up WinterPark or Copper. Both have tons of variety for many levels of skiing. Also, I've never had a bad snow day at either. (Been to each place 3x's)
@ WinterPark you should ski the Parsenn Bowl - don't be intimidated, even if it kicks your a** you'll still always talk about skiing it. Sleeper is a nice long fun run as well. Also the Drunken Frenchman is a must ski run...
@ Copper you will always find fresh pow in Spalding Bowl, just follow the ridge as far as you can, be patient and don't drop in too soon! It's well worth the push. I always had good luck skiing off the Super Bee or American Eagle lifts.
Don't waste your time at Breck, it's just a name w/ over rated skiing. Keystone is a great place if they've had recent snow, I'd definately go back, but it can be pretty hard on your skiis if they haven't had much snow.