That sounds like a good problem. I'm also planning on going through some of Project Euler and some Bioinformatics problem sets.We had a subject study session last week where we had to simulate an average speed check, taking a license plate and the times recorded entering and leaving the monitored section of road; this was pretty trivial to get going but it was a nice challenge for someone who has rarely used Python and can be extended to make it more difficult.
You could make a script that will take a file with a list of ISBN or UPC codes, decode what they are (lookup online perhaps?) and output a list of what they are, that'd be a neat little script. If you get a barcode app for your phone, you can then bulk scan all your books (or whatevers) and bam you have a list of all your books, no typing required.