First, let me say how much I like this widget! It's just what I was looking for. I really dislike tag clouds, and I like to save space on my websites, so using a drop-down list is perfect for me!
I have a simple feature request: It would be very helpful if the administrator could change "Select Tag" to "Select Keyword," "Select Label," or whatever word the admin prefers in place of "Tag."
The word "Tag" is confusing to a lot of people, and even though this is the word that WordPress chose to use, it's not the best choice for site visitors. I use "Keyword" instead of "Tag" on my sites because I think that's easier for most people to understand.
I edited the plugin and manually changed "Select Tag" to "Select Keyword," but of course, this will break with the next update of your plugin. It would be great if you could add a field so that we can easily replace "Select Tag" with whatever text we want, and have our settings remembered across updates.
Thanks for considering my request, and for all your hard work!
All the best,