Deploying a .NET workflow onto a SharePoint List

1. Copy the DLL your workflow creates from the build directory ( inDebug) to the Global Assembly Cache (GAC)
2. Create a directory in the features directory [C:Program FilesCommon Filesmicrosoft sharedWeb Server Extensions12TEMPLATEFEATURES] and drop both the feature.xml and workflow.xml files into the directory.

3. Install the feature on your farm, using the following command line statements
stsadm -o installfeature -name DocumentMoveAndShortcut

4. Activate the feature to a site collection

stsadm -o activatefeature -name DocumentMoveAndShortcut -url http://moss2007win2008

(or by going thru the site collection settings:
Activate the newly installed feature by navigating to the "Site Collection Features" page, under "Site Action" -> "Site Settings". Scroll down until you see "New Task Workflow", and click "Activate":)

From:

http://vspug.com/andynoon/2008/02/06/sharepoint-2007-workflow-with-visual-studio-2008/
http://philwicklund.com/archive/2008/02/12/deploying-a-net-visual-studio-workflow-into-a-sharepoint-list-in-10-easy-steps-part-2-of-2-deploying-the-workflow.aspx