This is a handy tool that you can use to browse elements by their workset assignment. You can also browse by category or element class. You can then select multiple items from the tree and then click the "Select Elements in Model" button to select them for further editing purposes.
Update 5/8/2016: CASE and the CASE Apps website are no more but, courtesy of WeWork, the CASE Apps are now open source. They may be accessed on GitHub.