I have the Logitech G27. It's probably the best when you consider the price and what you get. There are a lot of better wheels out there, but you can pick this up for $200-250 and you get a solid wheel, pedal set with clutch and a shifter. At some point I'd like to upgrade to the Thrustmaster T300. That one has a fantastic base but it's also $400 and it comes with crappy pedals that I'd probably want to upgrade to something else like a Fanatec pedal set.
So really it just depends on your budget. If you want to stay on the lower end, I highly recommend the G27. I wouldn't go for anything cheaper than that as you'll really start to sacrifice quality. If you have plenty of money to burn, there a lot of fun options to look at.