I kind of adopted plugin Cache Images whose original author was infamous Matt Mullenweg, co-founder of WordPress. Since I needed this functionality for my own needs, and this (and all similar plugins) was outdated, I rewrote it and send my changes to Matt who in turn gave me rights to update this plugin in wordpress.org SVN repository.
You can now download it from here.
With my new plugin, Gravatar Signup Encouragement, I had a problem with translation of string that is used only on activation.
That string contains default message that is saved in database. No matter what I tried, it would always save original string, not translation.
After asking question on wp-hackers mailing list and exchanging several replies with Otto, I found solution for this. In your function that is used in register_activation_hook, you need to again use function load_plugin_textdomain, even if you loaded it already in init. It should be used before any string.
So if you encounter this problem, you know how to solve it.
Don’t forget to try my plugin mentioned here, Gravatar Signup Encouragement.
Gravatar Signup Encouragement is my first publicly released plugin for WordPress. I got idea to write it after reading comments on post on Weblog Tools Collection titled “Why Is Gravatar Still Not Mainstream”. At that same day I made first version of plugin and posted link to it’s download page as comment on post waiting for responses but comment never appeared.
For last couple of weeks I was doing slow rewriting of plugin while adding new features and finally decided to release it publicly and to add it to WordPress plugin directory. You can now download it from here.