IMac 2008 Core 2 Duo does not list the bootable USB stick in the boot menu

A similar question was asked over at Programmers.SE, though it was about iOS development. Some might say that's not the same thing, but Photoshop is a robust application that allows you to install some very heavy-duty plug-ins and it has some of its own as well. The consensus could be gotten from the top two answers (mine, which has the higher vote count, and the other which was accepted):

Mine with 5 votes:

...leaving aside price, I would recommend a MacBook Pro for any serious development work instead. A MacBook Pro is more easily upgradeable to suit needs than an Air (if it is even upgradeable at all). The Air seems more targeted to lighter-weight uses.

Accepted with 4 votes:

It's obviously not going to be the fastest machine but it's perfectly suitable.

I'd say the 13" over the 11" because reasonable screen size is a big deal for development, and it can go up to 4Gb RAM rather than 2Gb (absolutely go for the 4Gb RAM model on day one and if you can afford it the faster processor as I suspect upgrading later isn't something Apple will be pushing).

Yes it's got limitations (basically the same as any laptop - essentially screen and power are limited next to a desktop) but I have the new one and it's entirely workable and I know others who use them (and used the old MacBook Air) day to day with no problems.

I, personally, still wouldn't recommend the MBA for any type of development work, web or otherwise. I've yet to do anything developing for iOS that causes me to bog down my machine the way Photoshop can and will.

rEFIt is a useful utility for selecting boot partitions that don't necessarily show up normally (Linux bootloaders, incomplete installs for example, or if there is something out of sync with the boot sectors).

You could use it here to see if it can recognise your USB stick, you could also use it to boot Windows from FireWire if that's at all useful.

You'll need a second usb stick to run it in 'live boot' mode, if you don't want to have it installed on your system, but it's pretty small so even 20MB is enough. Download the disk image and use Disk Utility to clone it onto your second usb stick, then boot with option held and it will appear.