I\'m using asp.net 3.5, my solution currently has 2 projects, an API class project and a website project, within the class project I have a resource file named checkin.resx.
Not sure if this will solve your problem but have you looked at the HttpContext.GetGlobalResourceObject method?
I've used it to access resources in the web project, from class libraries in a framework project - so perhaps you will have luck in using it the other way around.