<p>I know about code-behind files, but what is the best real-world way of Designers that are using DreamWeaver or other Design Tools to work with Visual Studio programmers?  </p>

<p>For example, say you have a basic website with user interface forms hitting the database... the database work is definitely done by the developer but how to tie the designed forms with the database coding or client-side logic that may involve events on controls, or other GUI related tie-ins.  Are the graphic designers also controlling application flow?  There seems to be a large disconnect that needs addressed - especially when it comes time to tweak the design after it's been implemented.</p>

The best way is to make sure that your designers have some knowledge of what kind of HTML they will be working with.
Every ASP.NET developer is aware of MS-HTML, that lovely nesting of HTML tables, but designers aren't. Designers have their own requirements to meet and they'll do them in the best manner possible. Sadly it's not often good for us.
I am always frustrated when I receive a design from our UI team which shows radio-buttons nicely layed out in a grid using floating div's. Then I have to shatter their dreams that no, I can't generate you that HTML (ok, I can with the use of ControlAdapters, but every time they are different designs!).
Try and have a 90%/ 10% rule, where 90% of the design is done before the ASP.NET starts and the 10% is done once the ASP.NET is completed, and done against ASP.NET generated HTML.
And make sure you're using source control! Code doesn't exist unless it's in source control! And thanks to the latest TFS PowerTools there's a lovely Windows Shell integration component so you don't need to use VS to check in and out now more :D