I've been looking at Tracmor (
Tracmor :: Open Source Inventory and Asset Tracking Online) for this type of application. It's set up more for warehouse management, but it includes the ability to add custom fields, and
track assets and inventory based on location. You can also attach files to individual records, or types. As sk8rsdad said, most barcode scanners will input text in a field for you, so you can use that to enter in asset ids into the
system. You'd just need to figure out what you want to do for asset tags. I can't say I have the
system in place yet as time hasn't been available, but we're hoping to eventually keep better tabs on repair and maintenance of equipment, as well as location. I work for a church that is planning to move towards multiple campuses, and we've also been partnering with neighboring churches to share resources. So having the ability to keep
track of where things are moving and who is moving them is appealing.
Tracmor has a hosted option (monthly fee), but the software itself is open source. If you have a webserver of your own and a
bit of patience, you can run it yourself for free.