Reliever free agents are, as a general rule, bad values -- reliever performance is so volatile due to their small workloads in any given year and the fact that relievers get hurt just as often as starters do (which is funny given how often teams put pitchers who can't stay healthy as starters in the pen, and then work them back-to-back-to-back days, as if that posed less risk to their arms).
That said, relievers will be signed (and traded) this offseason. Here are the best and worst values out there.
Best values
Jesse Crain, RHP (Free-agent ranking: 40): If healthy, or willing to sign a deal with a tiny base salary and plenty of incentives based on appearances, he might be the steal of the market, as he was in the midst of his best season before his shoulder went all China Syndrome.