http://term.ie/oauth/example/index.php is a live example of the php code found in http://oauth.googlecode.com/svn/code/php/example/.
The endpoints are:
http://term.ie/oauth/example/request_token.php
http://term.ie/oauth/example/access_token.php
http://term.ie/oauth/example/echo_api.php
The consumer key and secret are:
Consumer Key: key
Consumer Secret: secret
The tokens returned are:
Request token: requestkey
Request secret: requestsecret
Access token: accesskey
Access secret: accesssecret
I tested it with it's own client code at http://term.ie/oauth/example/client.php and it worked with HMAC and PLAINTEXT signature methods.
RSA signature would require the public and private keys used in the test server found here:
http://oauth.googlecode.com/svn/code/php/OAuth_TestServer.php
For a quick and dirty test this'll probably work, if you're worried about using someone elses server, it should be fairly easy to deploy the code from http://oauth.googlecode.com/svn/code/php/ locally or on a server you have access to that is running php.