I\'m using xUnit with the ReSharper test runner and the xUnitContrib resharper plugin.
When I have a long-running test, I\'d like to be able to output some progress
The easiest I've found is to utilize log4net and create a console logger. Along the way, as you're running, you'd call logger.Info("info here"); or log.Debug("info here"); - really whatever your preferred logging level - and the output will show in Resharper Unit Test Sessions.
Read more about the log4net framework on the Apache log4net homepage. The configuration examples will also be invaluable.