By Jessica L. Anderson, Associate Editor June 1, 2010 If you've ever bought a used car, you know how painstaking the process can be, from searching endless listings, driving from dealer to dealer and -- the most painful part for many people -- haggling to get the best price. Carsala, a new used-car buying service, does the dirty work and may save you money.It works like this: Call or log on to the Web site and enter the make, model, year range and so on. You can search just in your area or nationwide. Carsala will then send you a report listing cars that fit your description. It removes any damaged vehicles (wrecked or flooded) and cars from dealers with bad business practices. Carsala's system also gives every car a score based on how low the price is, the value relative to other prices for the same vehicle, and how long the car has been on the dealer's lot (a measure of how willing the dealer may be to lower the price). You can select up to 20 cars for Carsala to negotiate for you, including vehicles you have found on your own. Professional negotiators take over to haggle and get the final deals in writing. You get another report with the negotiated deals and can go for a test drive and complete the transaction. The cost is 20% of the savings off asking price, capped at $300, for up to 20 vehicles. So if the asking price is $15,000 and Carsala negotiates a price of $14,000, you pay $200 -- 20% of the $1,000 difference. Until October 1, 2010, Carsala is offering a $99 flat fee to Kiplinger's readers for negotiating up to five deals. Use coupon code KIP1E.