Does the visual studio development server have an equivalent IIS app pool idle timeout setting? If so, how do I change it? I'm having trouble keeping my user's session open while running in a development environment and wonder if this could be the problem.

You can set the timeout in sessionState in the web.config:

<!-- language: lang-xml -->
<system.web>
    <sessionState mode="InProc" timeout="30"  />
</system.web>

But changes to this value will also get deployed with your application. Another option would be to use a conditional compilation preprocessor directive and override the session timeout on session start in global.asax:

<!-- language: lang-cs -->
void Session_onStart(object sender, EventArgs e)
{
    #if DEBUG
        Session.Timeout = 6 * 60; // 6 hours
    #endif
}