In Nepal, using your bank, cash or atm card (as long as it's a Cirrus, Plus, or Visa), you can usually obtain rupees at a bank machine in Kathmandu. The machine will not give you dollars, or any other foreign currency. Sometimes, foreign cards dont work in Nepal. The most international bank is Standard and Chartered, and if you plan on using a credit card, you might ask your company to check if your card will work at S&C.
In Tibet, there is a new cash machine in Zhangmu (just across the border from Nepal), hopefully it's still working. Those of you going to Tibet may wish to consider bringing only dollars or changing all of your currency into local currency in Zhangmu, upon crossing into Tibet from Nepal.