p.pngpoxoq for patents
for an extremely fast and reliable patent download

Useful links

Open Patent Server (OPS) - Authentication
Open Patent Server (OPS)
EPO fair use charter
Registration page

Patent databases
Espacenet - The free, online EPO database
European Publication Server - The primary source of information on published EP patent applications and granted EP patents
Depatisnet - Electronic patent document archive of the DPMA, with roughly 66 million patent documents worldwide
Search Tool for Patents (USPTO) - Search tool for US patents and published applications
Swissreg - Swiss register of patents (including SPC), trademarks, designs and topographies
Patentscope - WIPO search tool for international patent applications

Online services
European Patent Register (Epoline) - Online european patent register and online public file inspection
Patent Application Information Retrieval (PAIR) - Information regarding US patent application status
Trilateral CCD - Common Citation Document (CCD) application by the Trilateral Offices

Inpadoc (raw data resources)
Raw data - Description of raw data products and test data
Coverage - Useful tables and statistics, coverage and codes

Classification
International patent classification (IPC)
Cooperative patent classification (CPC)
United States patent classification (USPC)
F-Terms/FI classification (Japanese classification)
FI/IPC concordance search

Patent offices and institutions
European Patent Office (EPO)
World Intellectual Property Organisation (WIPO)
German patent and trademark office (Deutsches Patent- und Markenamt)
United States Patent and Trademark Office
Swiss Federal Institute of Intellectual Property
Patent offices of EPO member states
Other patent offices

Other useful information
List of legal status codes
List of kind codes
Glossary of patent terms
JP patent number format after rekey Epoxy site | EPO concordance table (Number format concordance - publication numbers)