InfoJus- Instituto de Investigaciones Juridicas  
Offers Legislacion Federal Mexicana, a full text of Constitutions (federal and states), Codes, Laws, Jurisprudence. Vernacular.

Cámara de Diputados
The Mexican Congress and Legislación Federal de México (CDDWeb) contains the whole Mexican legislation. If you click on Consulta Textual a la Legislación you can obtain laws published in Diario Oficial in pdf format.

Diario Oficial (1994-) in full text at the National Law Center for Inter-American Free Trade - Mexico.  IP access.

Lexis
Mexican laws and jurisprudence: Federal Laws, Civil Code, Penal Code, Commercial Code, Mexican Tax Laws, Labor Laws, Mexican Federal District Laws, State of Mexico Laws (all available within one month of publication).

VLex
Access to legal journals the Official Gazette, codes, full text legislation, cases. IP access.

Taxation and Investment in Mexico -- IBFD database. IP access.
This IBFD service gives detailed, accurate and practical information concerning the tax system of Mexico. Commentaries and Mexico's tax treaties.

Guides:
An Electronic Guide to Mexican Law by Francisco Avalos and Elisa Donnadieu
Mexican Law by Prof. A Vargas who also wrote a Guide to  Electronic  Resources for Mexican Law