Yes, this is a standard feature of the platform. Please be aware that changes caused by workflow will also call triggers again, so beware of infinite loops.
Here situation: I have some object get by SOQL query, in my class I chnge value in some fields. Is is possible to somehow get workflow rules entry criteria and check if this object after my changes will fire those workflows? Ofcourse without updating this object or starting those workflows actions.
Please see order of execution here: http://www.salesforce.com/us/developer/docs/apexcode/Content/apex_triggers_order_of_execution.htm
Sorry - I might wasnt be clear enought.
Here situation:
I have some object get by SOQL query, in my class I chnge value in some fields.
Is is possible to somehow get workflow rules entry criteria and check if this object after my changes will fire those workflows?
Ofcourse without updating this object or starting those workflows actions.
No you cannot do this. WF rules will check the entry criteria at runtime.