As of the 1st of September, the TRIP database has reverted back to free-access for unlimited searches. Try a search at http://www.tripdatabase.com/.
The aim of TRIP is to allow health professionals to find the highest quality material available on the web.
TRIP is kind of metasearch engine that simultaneously searches a wide range of evidence based health resources such as guidelines, systematic reviews, evidence based medicine journals, clinical answers services, CATs, evidence summaries, etc. It also searches a range of images collections and patient information sources.
You can find out more about the aims, scope and methodologies of TRIP at http://www.tripdatabase.com/AboutUs/Index.html.