I bought an HP LaserJet 100 MFP M175nw. It's supported by hplip but only in version 3.11.7 and later. Debian Squeeze has version 3.10, so I upgraded my Debian installation to Wheezy. Installing hplip on Squeeze from Wheezy seemed to break a lot of stuff, so I figured upgrading would be easier.
To use the printer, you need to install hplip (>= 3.11.7) and run hp-setup. It will try to download a binary file that's required to print. In my case, the download never started and the installation just lasted indefenitely. So I manually downloaded the required file from the HPLIP project page. The file's name is hplip-3.11.10.run. The installer allowed me to specify the path to the file, but in GUI mode it wouldn't continue without giving me a reason: the next button was simply grayed out.
In CLI mode, I found out that the installer expects the filename to be hplip-3.11.10-plugin.run.
I renamed the file from hplip-3.11.10.run to hplip-3.11.10-plugin.run and finished the installation.