The stars must be in alignment. Three of my favorite agents have recent posts on writers who've received multiple offers of representation. Strung together, the posts are a How-To manual on gracefully handling this bounty of riches.
Let's start with Jonathan Lyons who set the subject up for us with his post on October 24 here called "Term of the Week: Beauty Contest." (You'll need to scroll down since Jonathan's posts are stored by month instead of by day). He defines the term "beauty contest."
Then go to Nathan Bransford's post here in which guest blogger Ginger Clark talks about how a writer SHOULD respond when s/he receives multiple offers for representation.
Finally visit my own agents' blog at BookEnds here and read what Jessica Faust has to say about the subject from the agent's side of the beauty contest.