Content dependent on the IP of the viewing user Is there any drupal module for implementing such behaviour? 
I want to display content especially selected for the user, based on her localisation/IP.

Can you propose some solution?

For example, for a side bar I would like to have a set of filters:


in case of IP in mask xx.xx.xx.xx display side bar A
in case of IP in mask yy.yy.yy.yy display side bar B
in case of any other IP display default side bar
I think that this depend that you are looking for. See this information if you want to hide a block according certain conditions http://drupal.org/node/134425 (you can custom your php using $_SERVER['REMOTE_ADDR'] to get IP address)

If you want to show or hide whole sidebar, I think that you can make this in template.php (in your theme), adding with php your IP condition, and according the result of condition, set (and/or unset) regions. See this for more/related information http://drupal.org/node/539488