Here's a simple scalar udf that gets the last day of month(LDOM). While the code is not "obvious" I don't consider the obtuse syntax a readability issue because it's well tested and commented in my environment-- and it's off in a udf.

CREATE FUNCTION [dbo].[udfLDOM] (@dd datetime) -- in: datetime out: LDOM (with time component stripped off)

RETURNS datetime AS BEGIN

RETURN dateadd(day,-1,dateadd(month,1,dateadd(month,datediff(month,0,@dd),0)))

-- NOTE replace the line above with a modded version of the last line of code on the previous post; it does it in 2 function calls instead of my 4!

END

BE AWARE udfs can dramatically slow your code if you are processing a large resultset. If you are doing this to set a page header or similar-- not a problem. But if you are SELECTing 10 million rows, each of which has a date and you are calling one or more udfs it may be time for a nap.

To get the day of the week "name" for SOMEDATE:

SELECT datename(weekday, SOMEDATE )

If you have to do this all in one step you could put both steps into another scalar udf (but then you'd need to collapse the date and the character day name into a string) or a stored procedure with 2 OUTPUT parms. But how you need to use this routine would dictate which if either of these is practical.