Patents

Patents are another good infomation sources. Here is a list of patents searchers:

FREE PATENTS ONLINE

In this searcher you can not only look for patents also you will find non-patent literature, blogs and law cases.

EPO

In European Patents Office you could not only find pantents but also all the information about how to create your own patent.

DELPHION

Subscription is needed but in their home page they said you can search 54 million patents worldwide.

GOOGLE PATENTS

Google Patents indexes patents and patent applications from the USA.