One of the things I'm most proud of to have ever developed is my Astronomy Picture of the Day
Even though I created the scripts for this back in 2003 I still get occasional mail about this. Today someone called Trevor Sayre mailed me he was inspired to create an actual application to do the same thing.
You can download the app here: http://bluetain.com/downloads/FetchAPOD.dmg
Although I haven't seen the code for the app I can confirm that it works on my Mac and that it doesn't appear to contact anything else than the Astronomy Picture of the Day pages. If all this scripting stuff and editing CRON files is a bit over your head you might want to give this a try. You will need a Mac, the app appears to be a Universal Binary so it will probably work on older G4 and G5 based machines.
Here's Trevor's mail:
I saw your APOD to Desktop Perl script plus Applescript set and decided to make an app to do the same. I even mashed together a nice little icon for the app. You can, of course, set the app to run at start-up if one wanted to have the background set to most recent with any reboot. As well, you can just have it lying around or on the dock and run it to have the background updated. Thank you for the inspiration and I hope you like it! Feel free to post it on your site if you'd like.
I am aware that since my scripts were written there have been a number of apps that do the same thing on sites like MacUpdate. I haven't tried those but then the developers never contacted me.
I'll keep using my own scripts as they've been running perfectly every day for 5 years straight but it's cool there are options.
Update: Trevor mailed me that he'd be happy to release a slightly different package so you can see the applescript that does the real work: http://bluetain.com/downloads/FetchAPOD.zip
It's pretty elegant I must say and a lot less hassle than my perl + osascript combo. The picture is downloaded to the ~/Pictures folder, to prevent flooding the system it's named the same every day.
I also misspelled his last name which is unforgivable but which I have corrected above.