If you want free stuff..

Route planning + moving map - Plan-G - Great tool to use but i mainly use it for GA flights
http://www.tasoftware.co.uk/planG.htm

Route Planning for CDU/FMC's, Route Finder - I tend to use this one a lot with the 757 but it helps if you have the sid/star charts as well :)
http://rfinder.asalink.net/free/

Free real world weather addon - FSRealWX Lite - Great easy to use addon with lots of features, use the DEV version as its more up to date and has a lot of bug fixes in it
http://www.hanse-coders.net/index.php?page=self&id=1