There are a few possibilities:
Was the new rim correct for your make and model?
The offset of the rotor may be different on the new rim. This would cause your caliper to bind.
Does your rotor heavily favor one side of the caliper opening?
Lift your front end. Does the wheel spin free?
Loosen and inspect the caliper/brake pads.
Did you inspect the wheel bearings on the new rim before installing the wheel?
Pull the wheel and inspect the bearings. A bad bearing can be extremely dangerous for a rider.
Related Videos: Sealed Wheel Bearing Replacement Check the tracking of your rear wheel. Make sure you have equal adjustment on both adjusters.
Check your neck adjustment. If the preload on your neck bearings is too loose, or over tightened; your ride will feel unstable.
Steering Head Bearings Lubrication
Have more questions? Check out the Tags here and our Q&A index page to find some answers here.