Is there a way to test logging in to a site with open id using selenium?
In selenium all the tests live in the server, so once fill the open id url in the appropriate field in the web page and am taken to the 3rd party web page for entering the credentials my test can't run any more.
Is there a way around this?
Yes - use Selenium RC. It gets around the cross-domain problem of basic Selenium Core and allows you to script against multiple sites.
I guess, technically speaking, you could include a really dumb OpenID server on your testing domain, but Patrick's suggestion of a testing framework that supports cross-domain operations sounds like a much better idea.
Although, I guess that depends on what you're trying to test. It could be that using a third party OpenID server is bad for your tests, because a change to the UI of that server could cause your tests to break. Or maybe you want to make sure that your code is interoperating correctly with that server, in which case using the 3rd party is exactly what you want to test.