First install the bookmarklets.
The PushPopURL service is quite simple. You push the URL to the service of a website you want to come back to later. Later you can either POP the next URL from the service and go to the next stored website or you can view your list of websites on the service and send them to other more sophisticated services for archiving or sharing.
Think of PushPopURL as your open browser tabs in the cloud that you can use from anywhere.
There is now an iPhone interface for the queue. From the iPhone you can browse the urls in your queue. I haven't figured out the best way to do other things from the iPhone interface quite yet, suggestions are welcome. Also there is a new bookmarklet, Delete, that will lookup the current URL in the database and delete it from your queue and then return you to the queue listing. This is useful when you are browsing your queue and don't know you want to delete it until you read it.
I've removed the Share This and replaced it with del.icio.us. It is much faster and I plan on making what service you use configurable. Also, there is now a history of all urls that you PUSHed. Also upgraded the PUSH to use a popup so the page doesn't need to be reloaded -- much faster.