Microsoft Works (wps) Documents aren't recognized by the native OpenOffice.org version of OpenOffice.

Update: Ubuntu has a libwps package that provides the functions to convert wps files and the Ubuntu version of OpenOffice will open a WPS natively (thanks to Andrew the libwps author for his comment letting me know this. When I first tried to open a WPS document on Ubuntu I had the latest OpenOffice.org version 2.4.1 of OpenOffice on my box not the Ubuntu version so I missed the Ubuntu native functionality).

However if you don't run Ubuntu you'll need the libwps-tools package to convert your wps document.

To install:
On Ubuntu / Debian
sudo apt-get install libwps-tools
On Fedora 8 etc
You will need to download and rpmbuild the source rpm or do the ./configure ; make ; make install three step from the source tar.gz both the source rpm and tar.gz file are available from http://sourceforge.net/projects/libwps/

Then to convert:
wps2html TheWPSDoc.wps > TheWPSDoc.html

You then open the html file as normal in OpenOffice and convert it to whatever format you want.

Microsoft provides a "Works 2000 Converter" for installation along with it's Office suite but that doesn't help people who don't have Office installed.

However the libwps tools have been ported to Windows and you can get the Windows binaries by downloading and unzipping the latest libwps-tools-0.x.x.zip file from Sourceforge.

To convert launch a command prompt (cmd.exe) and then cd to where you unzipped the tools and run:
wps2html.exe TheWPSDoc.wps > TheWPSDoc.html