On web servers or desktops running linux you can have the trunk versions by svn command but on windows there is no easy way of doing it.
Tagged versions are easily available but for trunk versions there is a trick by which you can download the zip file of the latest trunk versions of WordPress, bbPress, BuddyPress or infact any other script which is managed by Trac.
Visit the Trac pages :
- WordPress : http://core.trac.wordpress.org/browser/trunk
- bbPress : http://trac.bbpress.org/browser/trunk
- BuddyPress : http://trac.buddypress.org/browser/trunk
If you scroll down to extreme bottom of the page then you will find a link to download the zip file of the latest trunk version.
If you need any kind of help, then let me know through your comments.