I know I was first a little hesitate about recommending someone getting a second cat when the current cat is two...but being the mom of two cats, I can't see going down to just one.
Especially like 2kitties mentioned, going away for a weekend or even to work, makes it easier on them (and me)...they have someone to talk and play with and in my mind miss us a little less.

I don't know if our out of country friends have access to these, but I would not live without it now...the automatic litter box. It's the one where after they do what they need to do... and it automatically scoops it in a little bin after 10 minutes. It costs a little more (ok, allot more than the average), but the convenience of having one with multiple cats more than pays for itself. In essence, the cats always have a clean litter box.