The best I have found is either the eye-one display 2 or eye-one display LT.
They are both the same hardware just different software, with the display 2 being able to calibrate 2 monitors on the same computer, the LT can only do one, BUT the software is available to download to make them both the same. So buy the LT and download the latest software.
I have tried the Spyder series and Huey and couldn't get accurate profiles with them consistently. (Spyder have admitted that they have had issues with the tolerance of their sensors not being tight enough, rumer is they are releasing a Platinum version to address this.)
The choice is yours.
Kerso is selling all these now.