If you have only had it for a year and it's only running Mac OS X 10.5.8 then it must not have been new when you purchased it. Its successor OS, Snow Leopard, was introduced over four years ago.
A mid-2009 MacBook Pro in excellent condition, with original packaging, power adapter, original disks, new battery, and upgraded RAM is worth about $1000 at most.
Apple does not buy used Macs.
That's a different story. eBay is the best way to move it quickly, but be very wary of buyer fraud which has become rampant. Protect yourself by including screenshots of "About This Mac" in the listing showing its serial number (click the Version text twice), and include a photograph of the serial number engraved on its case. Be careful about shipping outside the country since a buyer may simply say he never received it, and it's difficult to obtain delivery confirmation for some countries. Buyers are King on eBay, and if a buyer is dissatisfied for whatever insignificant reason you must accept a return. If you refuse Paypal will seize your account anyway.
Other than eBay you can try Craigslist. CL can be a cesspool of ripoff artists and scumbags, but there are also many very pleasant and professional people looking for a good deal, and you can escape eBay's and Paypal's confiscatory fees. Agree to meet in a nice well-lit public location, let others know where you'll be, and bring a friend.
You will get the highest possible selling price if you restore it to as-built condition, and include everything it came with including the original box and packaging. A buyer wants to have the same experience as if it were new.
Follow these instructions: What to do before selling or giving away your Mac
In addition to the above:
- Remove any Open Firmware password if you created one: select Firmware Password in the Utilities menu in OS X Recovery.
- Remove any partitions you may have created, such as for Boot Camp.
- Once the sale is complete, un-register it in My Support Profile, if applicable.
You want to sell to a knowledgeable buyer. They are looking for equally knowledgeable sellers who have what they want. Given the fact it's a recent model, your competition is Apple's Special Deals page. Price yours sufficiently less than a comparable model and you'll get what you're asking.
99% of eBay sellers don't properly prepare a used Mac for sale. Be the 1%.