Ticket brokers are like stock brokers; they are great when they get you what you want, and terrible when they promise the moon just to earn a commission. There are a few companies I've used which not only deliver, but deliver even MORE than what they promise.
My favorite is the travel broker is Flight Centre. I had checked for flights online and over the phone before contacting them for a quote. Not only did they get me a better itinerary, but they beat the price I got directly from the SAME AIRLINE by $50 just to earn my business! The best thing was that I was able to pick up my tickets from a branch office close to my home the next day, without having to wait for mail delivery. Their prices are especially good on all international flights and vacation packages, but try them whenever you don't have the time or inclination to shop around for your travel arrangements.
For discounts on concerts, plays, and live events, sign up for Goldstar. The service is free and they offer last minute discounts ranging from 10-60% off on popular events like Wicked (they have a special right now for 40% off 25 select dates). I got seats at the Los Angeles Opera starring Placido Domingo for 50% off last season, so they offer something for every taste. Their newsletter gives you advance notice of events, sometimes even before public notice.
If you want (or need) the best seats possible for a reasonable price, then go with VIP Tickets. They do offer discounted seats to some venues like sports, but they are great for getting the best seat in the house if you are willing to pay a bit more for them (about double face value for the front center section). Sometimes it is worth the splurge because there is no other way to get those seats unless you know someone who works on the show. VIP will send out the tickets via messenger and they won't charge your card until the seats are confirmed. It's the next best thing to having your personal concierge.