There is another thread on this further in, but thought I'd respond here.

www.vacationstogo.com lets one select for "single". The cruises then shown include a single supplement. A few have 0%, lots are in the 20% range, and then on up. But usually much better than just paying full rate for the empty space.

Some cruise lines offer singles rooms, and again there is more on this in the other thread.

Regarding sharing with an unknown roommate - I've tried it. Once it worked quite well and we ended friends. But the second (and last time I tried it) the tour director had 4 singles. He decided to rotate us. One of the three was an unbelievably loud snorer. I travel with ear plugs and her volume was way beyond that. Also wanted to be my "new best friend" and tracked me everywhere. The second had just plain weird personal habits, and kept "forgetting" to leave the single key at the desk or not opening the door when I knocked to get in. The third was fine and in sheer desperation we asked the tour director to stop the rotation process and we roomed together the rest of the way. So - I decided 50% odds were way too low to mar another trip. Spare yourself.

Romelle