Publish a Login form or anything you want to this position.
The S5 Tab show holds up to 10 actual sidebar positions so you can publish any of your favorite widgets to one of the slides and keep your site clean and consolidated while giving it some eye candy. So simply publish the s5 tab show widget and then start publishing widgets to the positions in the tab show (s5_tab1, s5_tab2, etc)
After many months of requests we are happy to release the S5 box in a plugin form. S5 Box runs off of either MooTools or the jQuery Javascript library in a no conflictions mode so you should not receive any problems with other third party extensions you may be running on your site.
The plugin allows for up to 10 different S5 Box's on one page all via 10 sidebar positions. You simply add a class to any HTML element on your site and enable the corresponding box and you are good to go!