Try openjet.com. it compares fares on most loco airlines (except Ryanair) and even tells you about connection possibilities between them.
I could of course always recommend Dublin for some laughs...but Scottishladdies suggestion is good too!
You wont have many problems getting cheap flights from AMS
, You can try Easyjet.com, basiqair.com, smartwings.net (For prague flights), Aerlingus.com for Ireland, Meridiana.it for Florence, italy.. you're pretty much spoilt for choice really.
If you like an element of surprise, than go to klm.nl.. they have a cool last minute service called "click and go" which you will find under the "acties en aanbiedingen" menu (if you are on the Dutch site). This will offer flights leaving the next day to a small range of destinations that have spare seats. You dont know what they are until you log on (after 13.00 hours on the day before you want to fly), but it can be kinda fun that way! If you dont want to pay with credit card, you can even arrange to pick up and pay for your tickets at Schiphol airport before you depart.
Hope this helps, and enjoy Amsterdam... it is everything it is cracked up to be and more