I've got a Kestrel 2000 which is very good if a little pricey at £100ish. Gives all the usual speed in any variant you would ever need to know (MPH, Knots, etc etc), average, highest, and also gives temperature and therefore wind chill for the cold days ahead - pointless but it gives it something else to do....!!!! They also do a basic model and some more advanced versions too. Expensive but acurate - as in life you get what you pay for.
I only got one because I like gadgets....
Have fun.