This from Lifehacker:
Photovisi Creates Advanced Collages
By Jason Fitzpatrick, 4:00 PM on Sat Mar 21 2009, 12,082 views
Photovisi is a surprisingly sophisticated collage maker with an assortment of options for tweaking your collage to your liking.
Photovisi has eighteen collage templates for groupings of pictures ranging from only a couple up to 30 pictures. Once you select the pictures you can shuffle their order and crop them. On templates where there is some order to the photos, like a ring around primary photo as seen in the screenshot here, Photovisi lets you select which one will be the focus. You can bulk upload images from your computer or pull photos from Flickr.