Read OS X partition from Windows 7

MacDrive is what you're after. It's $50 for a CD or Download if that's within your budget, I can guarantee it's quality software.

For a free alternative as already mentioned, HFSExplorer works well, but it will not integrate like any other disk as you prefer.

If you are running Windows 7 under Boot Camp however, OS X 10.6 will include HFS drivers with Boot Camp to read OS X partitions from Windows.

You are looking for HFSExplorer: http://www.catacombae.org/hfsexplorer/

The version of Boot Camp that comes with Snow Leopard will contain HFS+ drivers for Windows. Rather than buy additional utilities, you might prefer to wait for the upgrade.

"Boot Camp now includes HFS+ read support that enables you to access the files on your Mac OS X partition from Windows. It’s read-only to prevent PC viruses from affecting Mac OS X, but you can easily save your work to your Windows partition and access it later from Mac OS X."

From http://www.apple.com/macosx/refinements/enhancements-refinements.html