A great source for discounts and freebies are the cab drivers. Most of them carry a large box in their cabs with tickets or discount coupons for shows, food and attractions. Just ask one. Like the OP said, the tickets4tonight locations are great too. But you'll need to get in line earlier on the day you want to see a show for a good ticket.
Vegas has alot of freebie stuff too. Like seeing the strip attractions-volcano, pirates and the fountains. There are also some free trams that you will want to take advantage of to save on cab fare and your feet. There is a tram that runs from TI to Mirage. Then you can walk through the Forum Shoppes at Caesars over to Bellagio. Bellagio has a tram that connects to City Center and down to Monte Carlo. From there you can walk to NYNY and across to Excalibur. Ex has a tram that connects Luxor and Mandalay Bay. These are all free trams as opposed to the Monorail that is about $7.00 a ride.