Update: Meerkat is down, we need another testserver.

You can test the XML-RPC subsystem using the xmlrpc_call utility which allows you to query XML-RPC servers from the commandline:

$ xmlrpc_call \
  http://www.oreillynet.com/meerkat/xml-rpc/server.php
meerkat.getChannels
meerkat.getCategories
meerkat.getCategoriesBySubstring
meerkat.getChannelsByCategory
meerkat.getChannelsBySubstring
meerkat.getItems
system.listMethods
system.methodHelp
system.methodSignature