SELECT  DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE())+1,0)),
Case
datepart(dw, DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE())+1,0)))
When 0 Then 'Sunday'
when 1 then 'Monday'
When 2 then 'Tuesday'
when 3 Then 'Wednesday'
When 4 Then 'Friday'
When 5 Then 'Saturday'
End 
as Day

declare @ThisDate datetime;
set @ThisDate = getdate();
select
    getdate() as CurrentDateTime,
    dateadd(mm, datediff(mm, 0, @ThisDate) + 1, 0) as BeginningOfNextMonth, -- Beginning of next month
    dateadd(mm, datediff(mm, 0, @ThisDate) + 1, -1) as BeginningOfNextMonth -- End of this month

declare @ThisDate datetime;
set @ThisDate = getdate();
select
    getdate() as CurrentDateTime,
    dateadd(mm, datediff(mm, 0, @ThisDate) + 1, 0) as BeginningOfNextMonth, -- Beginning of next month
    dateadd(mm, datediff(mm, 0, @ThisDate) + 1, -1) as EndOfThisMonth -- End of this month

 dateadd(dd, datediff(dd, 0, @ThisDate), 0)

select
        DT,
        FirstOfMonth = dateadd(mm,datediff(mm,0,a.DT),0),
        LastOfMonth  = dateadd(mm,datediff(mm,-1,a.DT),-1)
from
        ( --Test Data
        select DT = getdate() union all
        select DT = '20080214 14:37:25.867'
        ) a

DT                       FirstOfMonth             LastOfMonth
-----------------------  -----------------------  -----------------------
2009-09-03 11:23:58.503  2009-09-01 00:00:00.000  2009-09-30 00:00:00.000
2008-02-14 14:37:25.867  2008-02-01 00:00:00.000  2008-02-29 00:00:00.000

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