Looks like I'm going to be flying into CDG but staying at the Hilton Orly Airport, and was wondering if any of my FlyerTalk friends could give me info on the best public transport from one airport to the other.

Also, while I'm staying at Orly, is there convienent public transport to the center of Paris?

I know CDG and Paris very well, but have never been to Orly in my life. Thanks in advance for any advice/info.