Just a few API functions:

NetShareEnum
Retrieves information about each shared resource on a server or the local computer.

WNetGetConnection
Retrieves the name of the network resource associated with a local device.

WNetGetUniversalName
Takes a drive-based path for a network resource and returns an information structure that contains a more universal form of the name.

GetLogicalDrives
The GetLogicalDrives function retrieves a bitmask representing the currently available disk drives

FoxPro code samples (members area):

Defining currently available disk drives
http://www.news2news.com/vfp/?example=13&function=18

Mapping and disconnecting network drives in FoxPro application
http://www.news2news.com/vfp/?example=387

Retrieving information about shared resources on the local computer
http://www.news2news.com/vfp/?example=351

Retrieving a universal form for the drive-based path for a network resource
http://www.news2news.com/vfp/?example=317&function=490