I want to convert to SS.

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I have a Trek 4500 and I'm thinking about converting to single speed. It has verticle dropouts and I've seen a lot of articles showing weird derailer looking contraptions being used to tension the chain. Is there another "cleaner" way to tension the chain without extra parts?

You can attempt to file your drop outs in order to create some sort of chain tensioner.

You can also buy an eccentric hub. They're costly, but do the trick quite nicely. Had a guy come into the shop with one. Super easy to set the chain tension, and it opens up a world of singlespeed/fixed gear frames.

http://www.bikemannetwork.com/biking/p/WINDHUENOBLK

On the cheaper side of things, I did once see a guy come into the shop with a half link on his chain, paired with the proper gearing as a means of tensioning the chain. Worked just fine, but puts a limit on your gearing options.