This website is your friend. Has information on many, many types of catamaran dinghies. What to look for when buying a second hand boat etc etc... http://www.sailingproshop.com/catamaran_guide.aspxIn the 14ft size im surprised no one has mentioned Paper Tigers yet. For single handed sailing they are just about perfect, very light, small, easy to manage.
They are a pretty quick 14 footer, you can generally find a relatively good condition one for under $1400, maybe even under a grand if you're lucky. You can find ones in need of repair for under $400 though.
They are also an olympic class boat and can be as technical or as simple as you want to rig them and sail them.
If i was getting a cat though i probably wouldn't go with a hobie 16/14 because im not a fan of the banana hulls, they have a horrible tendency to pitchpole due to lack of bouyancy and surface area up the front.
In my experience:
Hobie 14/16's are cheap, single-handed and fun.
Hobie 18's and more technical but and you can push them harder than the 16's but you generally need two people when the wind gets up.
Nacra's can be quite pricey but are really fun boats, also need two people.
Paper Tigers are cheap and fun and single-handed.