Hello!
I am asking for help of this great community to educate me. I am in situation where I need to extend phisical ports in one of my high sites. The pricnciples of vlan is clear in setup, where I would use RB750 for example. but When I would use RB260GS becomes unclear.

Here would be classic setup. Router in base station is Cloud Core Router 1009-8G-1S. When I become short of ports I would add vlan-id=101, vlan-id=102, vlan-id=103 to port 8 for example, then port 8 from ccr is connected to port one on RB750, I add vlans whith id 101, 102, 103 to ether1 on RB750, then I create 3 bridges and bridge prots vlan101 and ether2, vlan102 and ether3, vlan 103 and ether4. create IP's and PPPoE servers on each port on CCR and I have nice isolated extension of phisical ports, where I don't need to setup vlan etc. on sector board. Could someone describe how to achieve same thing on RB260GS?
Thank you in advance!

Take a look on this SwOS configuration example, it should help you:
http://wiki.mikrotik.com/wiki/SwOS/Router-On-A-Stick