We have one.  It's called TopShelf, and it's now fully integrated with Salesforce.

TopShelf is a Warehouse Management Package that consists of a number of components.  It SaaS application that is hosted on our servers in our data center.  Those servers house the Web Application (Admin, Reporting, managing and more), Web Services and Database.  The final piece is the software that would run on a handheld device(s) and allows you to receive, put-away, move, pick, wave pick, pack, ship, build kits, cycle count, print labels, perform look-ups and more.

The integration package we have with salesforce (should make its debut to the AppExchange before Dreamforce08 as it's in review now) contains over 120 items (Classes, Triggers, Tabs, Objects, Fields, Reports, Home Page Components and more) to turn salesforce into an Inventory Machine.  It allows you to place orders as Closed-Won Opportunities and add products to it.  It allows you to enter Purchase Orders to purchase new Products.  It also tracks both On-Hand and Available(un-allocated) quantities which gives your sales personnel both a great entry point for orders and gives them a direct look to the inventory in the warehouse.

Now if you either use our SNAP API to integrate TopShelf to your accounting package, take advantage of one of our pre-build integration services to integrate into a QuickBooks GreatPlains and more, or even used one of the preexisting AppExchange applications to integrate salesforce back to you accounting... you now have a full system at a great price.

For more information: http://www.scoutsft.com/topshelf.aspx

TopSearch (our viewer only) is also on the AppExchange here: http://www.salesforce.com/appexchange/detail_overview.jsp?NavCode__c=&id=a0330000005Hzh3AAC

TopSearch is not our upcoming full integration, but just a viewer to see into topShelf.  The new full integration product is called "TopShelf for Salesforce".  So keep an eye out for it.  :smileywink: