in my village, there is a 500 x 500m block which just is white space at OSM.
I read there is free maps material from Bing and Yahoo which could be used to fill this gap - but how??
Is there a (semi-)automatic process to transfer missing info (roads, houses) from Bing/Yahoo to OSM?
The only material from Bing/Yahoo is the default Bing background imagery used by the editor to facilitate drawing roads. Actual road and house data cannot be transferred from Bing/Yahoo.
The only way to get data without doing a survey is if the local government has released the data into the public domain.
Here are some hints:
Yahoo Sat images are deprecated, so
http://wiki.openstreetmap.org/wiki/Bing is still a good source.
Read http://wiki.openstreetmap.org/wiki/Beginners%27_guide to get familiar with basic OSM schema
Chose an online editor like Potlatch2 or an offline editor like JOSM or Merkaartor to draw streets and objects from Bing images.
Read read read the wiki about editors etc.