A while back, I wrote a quick script to tag photos with the GPS locations by matching the times of the photos with the log from the GPS. I just found the application GPSPhotoLinker which does this really well.
I sometimes have quite rough bitmap images that I want to make into something nice and clean for a paper or a talk. This online service from Stanford makes a brilliant job of tracing bitmaps into vector images (and hence back to clean bitmaps at any resolution).
I missed not being able to print ”booklets” on the Mac in the same way I could under Linux – ie. 2-up, double sided, but arranged so that you could just fold the whole lot in half and get an A5 booklet with the pages in the right order. Then I found CreateBooklet which does exactly that.