Cycraguard look great, and bolt/bungy/cable tie onto the downtube. They keep your legs and front mech/chainwheels a bit cleaner, but if you go fast enough the spray thrown up by your front wheel will be blown back into your face anyway.
There are some that go through the front forks and stop some of the above, but personally I think they look crap. Look for brands such as Planet X or SKS, Marzocchi Fenders.
Buy some glasses instead, you'll look far cooler, and wear your mud with pride. Oh, and try and keep your mouth closed on farmland. Slurry doesn't taste too good.