I’ve been using Evernote for over 2 years (I checked. I thought it was longer, actually, since it’s such a regular part of my work process). I only recently started using it for moodboards. A tweet from @Evernote asking if anyone used it this way caught my eye, I responded, we emailed, and voila! My thoughts are right there on the Evernote blog as part of their Creative Series. Nice!
If you haven’t tried Evernote, you really owe it to yourself to check it out. It’s web-based, but there are also desktop, iPhone, and iPad apps that sync to it, and of course bookmarklets that make it easy to clip and save stuff to your notebooks. I’ve used it not only for moodboards, but for market research, read-it-later types of things, recipe collections, shopping research, wishlists, idea lists… the possibilities are endless.