Hi Rashid,
I would suggest you start with Craig Larman - Applying UML and
Patterns before referring to any online stuff.
Once you have grasped the fundamentals you can supplement your knowledge with various links available on OOAD.My favorite is
Cetus Links.
Also, please do a search in this forum for other good links on OOAD.I am sure this has been requested many times before.
-- Sandeep