The MDB tools project is an open source effort to create a set of software libraries and utilities to manipulate files in the proprietary JET 3 and 4 database formats (used by Microsoft Access 97, 2000, 2002-2003). Version 0.7 release candidate 1 was released in september 2011 on github.
The MDB tools include Gnome MDB Viewer (gmdb2), a desktop tool for viewing MDB databases on Linux. For MacOS X there is a proprietary application named MDB Viewer that also provides a graphical front end to the MDB tools library.
There is a Java port of the MDB tools library named Jackcess. Jackcess adds write support, but drops support for Access 97. It seems to be under active development as of 2010.