Possible tune-up races:

3/16: E.P. "Tom" Sawyer Irish Classic 10K. Register by 3/13. $35

This is pretty much a no-brainer. Right in town, right distance, cheap registration, somewhat familiar course. It has some grass, dirt, gravel, as well as asphalt, but nothing wrong with that.

3/30: Carmel Marathon Weekend 10K. Register by 3/24. $45

This seems to be the best choice. Alternatives are Caracole's Run/Walk for AIDS 10K in Cincinnati ($40 on Sunday, no deadline posted), or RunTheBluegrass 7 mile race ($100). The former is on Sunday - it might be good, if I shift my training by the required one day. The latter is very unlikely: it is outrageously expensive, and what an odd distance!