I tried Line Camera for iPad. The beauty touchup tool is cool. I also liked the design Chalkboard. Unfortunately the borders ("frames") seem to need to be purchased.
We used PhotoGrid for National Library Week. On iPad we took a picture of patron answers to a daily question board and arranged them into a collage. Then we posted to Flickr.
BTW Flickr upgraded this week, changing "sets" to "albums". Also, tagging is different. I couldn't figure out how to tag on the iPad, but was able to do it on PC.