Microsoft's Information and Support Sites:

http://support.microsoft.com/ Microsoft's support site, including the indispensable Microsoft Knowledge Base

http://www.microsoft.com/office/ Microsoft's Office area, with information about the Office products, including Access, and technical resources

http://msdn.microsoft.com/ The Microsoft Developer Network site, lots of information of interest to developers

http://www.microsoft.com/downloads/ Download Service Releases, Service Packs, Information, and Examples for your favorite Microsoft products here

Other Vendors:

Note: Most have Free Downloads, Goodies, and Information, in addition to the products they sell.

http://www.moshannon.com Black Moshannon Systems, home of the search and replace software Speed Ferret

http://www.databasecreations.com Database Creations, formerly Cary Prague Books and Software, carries a broad line of Access-related software and books (they also consult)

http://www.gfminc.com Greenwich Financial Modeling has the well-known Access to VB conversion program

http://www.rickworld.com Rick Fisher Consulting, author of the popular Find and Replace for Access

http://www.fmsinc.com FMS, Inc. has a comprehensive line of add-ins and utilities  related to Access, VB, and SQL Server

http://www.peterssoftware.com/ Peter De Baets has several add-ins including Shrinker Stretcher and Drag-N-Dropper