Where does macports install programs

If you use contents, it will tell you where they are.

Unless you performed a custom installation of MacPorts everything installed by MacPorts is located conveniently at

/opt/local 

if you perform a directory listing at that location you should see the structure for port installed programs which should be installed in bin or sbin directories.

user$ ls
bin     etc     include lib     libexec man     sbin    share   var 

As noted in the MacPorts Documentation

2.3. Install MacPorts

If you are using Mac OS X, you should install MacPorts using the Mac OS X package installer unless you do not wish to install it to /opt/local/, the default MacPorts location, or if you wish to install a pre-release version of MacPorts base. However, if you wish to install multiple copies of MacPorts or install MacPorts on another OS platform, you must install MacPorts from the source code.

To find where any Unix commandline executable is located, use the which command:

$ which bash
/bin/bash
$ which port
/opt/local/bin/port