I came across this really neat algorithm for resizing images by eliminating (or duplicating) the “uninteresting” bits. This allows you to change the aspect ratio without significantly distorting features like faces. You can also mark certain features manually to be preserved or eliminated. Watch the video. There is a port for the Mac with a GUI.
I’ve been using BibDesk on the Mac for a long time, but I guess some people don’t know about it. It is very good GUI interface to bibtex but it stores the data in ordinary bibtex files so you can easily alternate between the GUI and manual editing. The latest version allows arbitrary aliases and URLs to be added and these display as thumbnails.