Is there any way to hook into saving a plugins settings? I'm attempting to create a plugin that is going to create some basic fields/sections as a post-installation setup. I don't really want to create a full-blown CP entry so is there any way of just doing stuff when the user clicks "save" in the settings template?
Take a loot at the prepSettings() function of your plugin.

http://buildwithcraft.com/docs/plugins/plugin-settings