[tadol]

In the "old" days, they'd make them themselves - a hand turned drum with a inclined bed underneath, cheap, could be accurate, but earned the nickname "widowmaker" -

The Performax/Jet line are nice - the wider ones nicer not because of the extra width, but because you have more drum area to use before you need to change the paper. The drawback to them is because only one side is anchored, they tend to have tiny issues with parallelism between the head and the bed - nothing that would seriously affect most cabinet or furnituremakers, but potentially problematic for luthiers. Better units have heads that are fixed at both ends, and can be fine tuned to be absolutely parallel. Grizzly has a pretty nice one -

When evaluating any of these, make sure you have a dust collector that can move an adequate volume of air to pull all the dust, and has filters fine enough to trap it - without really good dust collection, the best sander units will be pretty much useless, but great dust collection can make the lesser sanders quite tolerable -