Corporate alternatives to DropBox for iPad
A search on the iTunes store for SMB file browsers finds something called - ahem - FileBrowser that sounds like what you need. Haven't tried it myself - although thinking about it something like this might be a help in my workflow. Did I just cost myself $3 by answering a question? 

It's at http://itunes.apple.com/us/app/filebrowser-access-files-on/id364738545?mt=8