Have you checked out the OER Commons? OER stands for "Open Educational Resources." It's a very cool new resource for educators, a virtual catalog of course materials that relies on its community of users to contribute, review and tag items.
So far they've got 6 entries for "invasive species," from a link to the Scientific American Frontiers Alien Invasion website to a case study of a marsh invaded by purple loosestrife. You can even set up RSS feeds for your favorite tags and keyword searches, to ensure you're kept up to date when news items are added that match your interests. Lots of great stuff there no matter which subject you are teaching or how old your students are.