Create Chatter post with mix of HyperLinks and text in the Body (in Apex code)

So, I haven't actually tried this, but here's what I would try first:

FeedItem myPost = new FeedItem();
myPost.Parentid = object.Id; //user's Id I'm assuming
myPost.body = 'Text here http://www.internets.com more text http://www.theinternets.com';
insert myPost;

Obviously, you'd have to get the Id of the object you're posting to and the links to the contact and opportunity.