Sequence Numbers in SQL server

Have you ever thoguht of generating sequential numbers? I guess, many of us had atleast once a scenario atleast for our reporting purpose to think about sequencing the records.

Here am going to explain how do I come across with various SQL server versions. We have something like IDENTITY (I will explain little more about this later) in all of SQL versions available. It is a kind of methodology given by SQL server to generate sequencing. How about when you do have scenario to generate the
sequence while you write a procedure.Here we go!!!

SQL Server 2000

SELECT
RowNumber = IDENTITY(INT,1,1)
,c.LastName
,c.FirstName
INTO #Customer_RowID
FROM SalesLT.Customer c
ORDER BY c.LastName ASC
SELECT * FROM #Customer_RowID

SQL Server 2005 and 2008

SELECT PurchaseID, PurchaseDate, ROW_NUMBER() OVER (ORDER BY PurchaseDate) AS 'RowNumber' FROM PurchaseOrder

SQL Server -(Denali)
In addition to ROW_NUMBER, there is something called Sequence introduced in Denali Version. I have not got any personal experience with the same.Hence am just giving a clue...