ToxSeek

ToxSeek is a meta search and clustering engine for environmental health and toxicology. It provides access to dozens of specialised search engines, including a large number of NLM resources, which is unsurprising given that it's the National Library of Medicine that's produced it. Unfortunately since I'm not any kind of specialist in this area I don't feel able to comment further, but if you are and have anything you'd like to say about it I'd particularly encourage you add a comment.