The Monteverde Cloud Forest is an amazing place! You can go on a day trip to Sky Trek  which is a zipline adventure and hike through the forest on suspension bridges. The Sky Trek attraction is a bit on the pricey side but once you go on the ziplines you will find it is  WORTH EVERY PENNY! There is one line which is over 2500 feet long and if you're in the area spend the money and go.

Other canopy tour companies include:

The Original Canopy Tour - here is a link to their information on Monteverde. The best is the newosh Extreme Canopy Tour.

Selvatura Park - has canopy tours and a lot of other activities. 

You can find information on the many activities and attractions in and around Monteverde at the official Costa Rica website

  The 2500 foot ride  

The 2500 foot ride (2)

The 2500 foot ride (3)

One of the suspension bridges