Some DateTimeExtensions (Links)

StartOfTodayInUtc

ToStartOfTimeZonesDayInUtc

ToLocalTime and ToUniversalTime

http://www.lostechies.com/blogs/joshuaflanagan/archive/2011/02/03/helpful-datetime-extension-methods-for-dealing-with-time-zones.aspx

FirstDayOfMonth / LastDayOfMonth

SetTime

AddWeekdays

http://dotnetslackers.com/articles/aspnet/5-Helpful-DateTime-Extension-Methods.aspx