Good search tips. The free reports are brief, about one paragraph, but useful for checking facts, and they provide 170,000 links to related WWW sites.
Importance is explained here .
They index only pages submitted to them, and they periodically re-index sites to discover and fix bad links. Also contains brief news. Their web search starts with 17 categories, but also current text search, news, maps, etc. Great for long phrase searches. The scores are then rated and listed based on these results.