The classification system is somewhat arcane, so you will still need to browse in order to get a feel for which classifications hold the patents you want to access. There are useful links to other patent bodies here, both U.S. and foreign, as well as a free weekly maillist update of PTO issuances which is yours for the asking. Prior art searches are available for a charge, but are not available on line. Good for finding patent citations by patent number and title that you may want to order in full later. Also accommodates keywords and anti-keywords.
Registration is mandatory.
With it you can download the front page of any patent in the database. Trademark searching is also available. Offerings include an online magazine, ideas mart, bookstore, and hot links to other Web innovation sites including technology transfer organizations. The service is free and aims to cover the U.S. and Canada. Not all links were functioning on my last visit.