Free Classification Links

USA

• USPTO's Manual of Classification
  (U.S. Patent Classification)

European

• ECLA
  (Nifty Tool for Searching ECLA Codes by Keywords)

International

• International Patent Classification
  (7th edition) (WIPO)

Other WIPO classification schemes

• WIPO Classification Schemes for Trademarks
  (NICE, VIENNA) and Designs (LOCARNO)