VueScan Scanner Software
I can't believe it took becoming a Mac user to discover VueScan way back in 2002. I downloaded the trial version on an old Mac, launched the application, and without issue scanned documents natively on a UMAX scanner that hasn't seen new Apple drivers since 1998.
You don't have to be a Mac user to appreciate this level of compatibility - VueScan also works for Windows and Linux. You also don't need a 15 year old scanner either, though if you have one, chances are good it will work with VueScan.
The TWAIN drivers typically used for scanning are bypassed entirely, which seems to be more effective in terms of program speed. Scanning via VueScan seems to be faster than when using native drivers in some cases. Most of us can get by with the basic preview, crop, and scan solution at the core of this application.
If you are a power scanning user there's an advanced version with a long list of cool features more comprehensive than I can document here. Lets just say, if you wanted to configure something about your scanner, this app can probably do it. Most of us probably have a scanner or two that still works from a mechanical standpoint, but is no longer supported by our most recent operating system upgrade. VueScan solves these incompatibilities on over 2100 different scanner models.
Registration permits you to use the application on up to four machines. The trial version watermarks scanned images. If you have a smartphone, VueScan Mobile is free for iOS or Android. [Win/Mac OS X/Linux $39.95 or $79.95]