IFM is something I hacked together a while ago, to help with mapping IF games. It produces maps in the traditional Infocom style, like this:
You can find the latest version of IFM in the IF archive. Dave Chapeskie, who had a large influence on IFM in its early years, created a web page about IFM, including some maps of actual games.
IFM is hosted on Bitbucket, so you can hack on it. You can also read the latest documentation.
IFM doesn't provide much of a GUI interface; that's not really my thing. But Gonzalo Garramuno has written another, more GUIfied, mapping tool called IFmapper, which can read and write IFM maps (among many other formats). It takes a few ideas from IFM and runs with them — notably the tool for creating maps from IF transcripts.