There is a new online version of the Global Compendium of Weeds available, and it's a big improvement over the previous version. The old online GCW, though quite an amazing repository of information, was a mere sampling of the over 20,000 species of weedy plants listed in the hard copy. The new online GCW has been updated to feature over 28,000 plants, and best of all, has finally taken a big step towards taking advantage of some of the benefits electronic media can have over plain paper. In the old online version, each species page had a list of references by number, pointing you to a ginormous web page of references where you had to look each number up - very similar to the hard copy. The new version has the references listed directly on the species page, along with the classification given to the species by each reference (endearing terms like "casual alien," "garden thug" and the standard "agricultural weed").
Whereas most invasive species guides tend to be region specific, the Global Compendium of Weeds truly has worldwide coverage. It was surely a massive effort to bring the GCW to a second edition, and the ISW gives kudos to Rod Randall for providing free online access to this valuable resource.