I could probably fill the entire Invasive Species Weblog just using posts about Hawaii. The islands are constantly being bombarded with new pests, but perhaps more importantly, the topic gets a lot of media attention there.
Back in May, someone discovered the Erythrina gall wasp (Quadrastichus erythrinae) in Honolulu - the Honolulu Advertiser has the story and a photo of the freaky effect they're having on their chosen host plants, including the native wiliwili (Erythrina sandwicensis). The newspaper also has a follow-up story here with a photo of the wasp.
Then in July, the Hawaii Department of Agriculture discovered the hibiscus psyllid, Mesohomotoma hibisci, on the island of Oahu (link has photo of species top right). It's the first ever occurrence of this species of this East Asian jumping plant louse anywhere in the U.S. That story doesn't seem to have made the news yet though.
Additional information for this post contributed by the USDA-ARS-Systematic Entomology Laboratory.