We have published the CMIP3 data as a collection of datasets into the gateway http://cmip-gw.badc.rl.ac.uk/.
I get an intermittent error when browsing using the "Search Categories" box:

  Error: Failed to convert property value of type [java.lang.String]
  to required type [int] for property limit; nested exception is
  java.lang.NumberFormatException: For input string: ""

This error appears sporadically and I haven't managed to work out what it depends on yet. Once a browse action succeeds it seems to stick and subsequent actions also work until either I log out or close the browser, then the error returns.