The Messaging Center is the next step.

Once you find members that interest you, contacting them is easy. Your note goes to their Inbox on the site and a notice is sent to their email letting them know. For those with the Option Pack, they can also choose to be notified by a text message on their cell phone.

If you don't have the time to finish a message in one sitting you can always save it to your Drafts folder and finish it later.

If you strike up a regular correspondence with someone, you can quickly add them to your Contact List to make it easy to find them in the future.