A while ago i created a small utility that allowed me to easily switch between users in a portal. This is extremely usefull if you are developing a module or a site and you want to test different permissions for different users.
The current version of the module allows you to select whether host users can be switched to as well. Doing this means that you will never have to log on to your site again...
NB: Never use this module in a live environment, as it will make your site VERY insecure!
You can download this module from http://www.codeplex.com/userswitcher, and vote for it on the DNN Forge Page