Transact SQL :: How To Number Rows In SELECT

I have a SELECT statement with multiple JOINs. I want to number the rows returned by this SELECT statement. What's the easiest way to do this?

My current SELECT statement returns this:

ProjectId -- TaskId -- TaskName
123  - 111 -- Do something
123  - 222 -- Do something else
123  - 333 -- Do one more thing

I want to return this:

ProjectId -- TaskId -- TaskName -- Sequence
123  - 111 -- Do something  -- 1
123  - 222 -- Do something else  -- 2
123  - 333 -- Do one more thing  -- 3