Don't you hate how your iPhone and iPod Touch can't store your entire library? Good news, it appears Orb (a winamp media slinger) will soon be compatible with the iPhone.
With this nifty software you'll be able to access all of your movies and music stored on your home PC wherever you are. Best of all, it should be free

Oh and because I know all of you will ask -- No its not released yet, just coming soon.
[thanks ericidel | via theregister]
Edit
For OS X users this has been around for awhile, but might as well mention it here in this thread. Use SimplifyMedia

[ame="http://www.youtube.com/watch?v=W0qxs-P6NFQ"]YouTube - Simplify Media for iPhone[/ame]