The biggest issue with older drives is reliability. You can use then for getting files from place to place, but with a power supply and everything they are not always that portable.
If you want to do it, I would use the biggest ones you have and use the old ones for experiments(want to try Linux? Install it on one of these
If you have any laptop drives in the bunch, they may make a good portable die to size and that fact that they can be powered off of a usb port or 2.
As for enclosures. If you do not want to deal with them, you can get a USB2 or 3 to SATA/IDE adapter, that will let you use the drives bare.
like this.(does not have to be THIS one, just what Google gives me)http://www.canadacomputers.com/product_info.php?cPath=48_19_797&item_id=038844
I have sued Vantec and Bytecc enclosures without issues in the past as well.
Remember for IDE drives, you have to set them to master with external enclosures and bare drive USB -> SATA/IDE converters. and you can not use SATA and IDE at the same time of those adapters.