QSL Routes 

IK3QAR
K4UTE QSL Manager Database
OE-1002419 QSL Lookup & QSL Info Page
OZ7C QSL Manager Database
Pathfinder
QRZ QSL Manager
QSL Managers Society
SM5ARL QSL Address Database
SM5ARL QSL Manager Database
SMIRK QSL Database
The Daily DX - QSL Manager Listing
WWW.QSLINFO.DE - the Internet's #1 QSL information search!

QSL Collection - Great history and much, much more

IRCs or Greenstamps? (W9OL)
Another IRC and Greenstamp chart (N6DHZ)
Another Greenstamp chart (K4HB)
Rückporto für QSL-Post nach Deutschland (DL6ZFG)

Currency converters
Oanda.Com
Postal Rates.Info
Postage Rates Worldwide