FileInfo.com - The File Extensions Resource

.NET File Extension

File Type 1	netViz Project File (Most common)
File Format	File
Common?	No
File Description	Project created by netViz Enterprise software, a set of programs that enable the visualization of data; often used for diagraming business models and IT infrastructures; can be published and viewed on the Web using netViz webView. Example projects included with netViz software are often called "Global Network.net" or "Global.net."
Program(s) that open net files	Windows: netViz Enterprise software

File Type 2	FileMaker Networking Module
File Format	Proprietary File
Common?	No
File Description	Module used by FileMaker Pro that enables various types of networking support; "FMTCP32.NET" is used for the TCP/IP protocol and "FMIPX32.net" is used for the IPX/SPX protocol; both files are typically installed with the FileMaker application.
Program(s) that open net files	Mac / Windows: FileMaker Pro

Information from FileInfo.com - The File Extensions Resource.
http://www.fileinfo.com/extension/net