there's a strange quirk in Photoshop that allows you to increase the size of an image by 110% at a pass with no pixilization - you can theoretically blow a thumbnail up to the size of a billboard with very minimal quality loss -
I even made an action for it that I linked to the <F12> key to do it as many times as I need - grab the action here:
http://www.graficalicus.com/download...hp?image_id=78 for Elements users:
(if you're an Elements user, you can also use this action - I made an installer for it, as well as several other actions - that will put it in your Effects palette where you can use it at will - all the free "Action Packs for Elements" are in this category on my site:
http://www.graficalicus.com/download...s.php?cat_id=8
If you want just the "110% Blast!" Action, get it here:
http://www.graficalicus.com/download...p?image_id=104
- the 110% Blast is also included in the "Handy Actions!" pack - these are all free downloads