The RISC OS Products Directory was set up by RISCOS Ltd. and was apparently last updated in January 2005. The new version, on RISC-OS.net doesn't contain as much general information as the RISCOS Ltd. version, but is reported to be slightly more up to date, and allows developers to add their own software to the database rather than having to request that it be added.
Of course, there are still other RISC OS Links directories out there, such as Google Directory Category, The ANS Filebase, Paul Vigay's Links Directory (which has just been overhauled again) and the now somewhat out of date (and similarly named) RISCOS.net.