I thought they would all work with a Mac Michael. I assume you refer to dedicated 35mm scanners (not flatbed).
I use a Canoscan FS 4000 US which is not a current model and Canon don't support it with drivers but Vuescan works.
The Nikon Coolscan series was pretty good for this. As you know, various flatbed scanners have holders for slides from 35mm upwards.
Some thing to remember:
A 35mm slide has to be scanned at a very high resolution to give a reasonable sized result, so for good results your scanner needs to be high-res (ideally 16-bit rather than 8-bit). That means software that can deal with 16-bit properly to make the adjustments to your image that will almost certainly be necessary.
You may need to deal with slides "popping" out of focus as the film adjusts to temperature changes.
A proper slide scanner can be very expensive, and the software may be "premium" too.
Have you tried going to a service bureau -- could be a lot less expensive?
Received wisdom has it (ie everyone on the internet says) that you get a used device from fleabay use the device and then sell it on without loosing much money.
Typically people only buy the device for a specific project and then sell.
Bureau scans are expensive for small numbers but the cost reduces for scanning in bulk. I have used R&K scanning services (Cornwall) and for 151+ the cost would be 50p each. http://www.randkphotographic.co.uk/index.htm
I find scanning individual slides slow, difficult to obtain a 'clean' scan and am doubtful about quality from a flatbed scanner. It would have to be a 'top end' machine with 'Ice' software to reduce dust and scratches. Doing that in Photoshop softens the image too much. The other consideration is quality of the slides. Some are difficult if not impossible to scan satisfactorily. Contrasty slides are the main problem.
Not that I've tried it, but projecting them and photographing them with a digital camera on a tripod could work. I have done this with old photographs; if you're using an SLR you can be jolly accurate.
Projecting onto a screen for shooting may not give the required quality. However using a digital camera to shoot slides with backlighting will be better. I sometimes use a lightbox for this with the slides masked to keep out stray light. Other alternative solutions here: http://www.srb-griturn.com/slide-copying-308-c.asp
Michael Corgan 