I have an iMac running Snow Leopard 10.6.8 and I own a HP ScanJet 3670 Scanner.
HP gave up attempting to support this scanner and the accompanying software years ago, but some people have figured out how to give it life again.
You computer is going to freak out if you try to install the software for the HP ScanJet 3670, but everything goes great if you install the same software but tell the installer you actually want to install it for the ScanJet 3690. Here is how you go about it.
1.) Download an old scanner multi installer from HP's FTP site:
2.) Install it. It is old junky software so be aware of a few things. After you put in your administrator password it'll act like it has stalled for a couple minutes (just wait it out). You'll select ScanJet 3690 after that. The software will also forcibly quit any applications you have open so make sure you don't have anything unsaved. If you are viewing this website it'll close your browser. After the installation is complete it will force you to restart your computer.
3.) Upon restart you'll notice two icons in your dock. If you are like me you don't want them there, so trash them. HP will do it's damnedest to force them back in your dock so go checkout your Accounts in System Preferences, find Login Items and remove both of the HP Scanning tools.
4.) Scan stuff. It should work just as well as you could ever hope.
I have read reports that this trick works exactly the same in Snow Leopard as far back as 10.6.2 but your mileage may vary. Anybody know if the ScanJet 3670 will work in Lion? Leave a comment about what Mac OS X system you have gotten the scanner to work in.