IKEA has pull out drawers for 24" deep pantry. I just installed one and they're great.

You don't want wire baskets, you want roll-out shelves as bordenh mentions. If your measurements are exact, you can use the Ikea drawers and drawer glides for the 24"w x 24" d pantry units. If your measurements are approximate you should take a look at Barker Door for highly customizable wood roll-out shelves and drawer glides. You can get whatever size you want.

Here is a link that might be useful: Barker

Another option for pullouts/interior drawers would be Blum's metabox line. You buy the drawer sides + glides, and brackets to attach the sides to the drawer front. Also, rear-mount brackets if you have face frame cabinets (not nec if your cab is frameless).

Then you cut your drawer bottom, back, and front to the exact width you need.

Here is a link that might be useful: Tutorial here (though they created regular drawers, while it sounds like you'll need interior drawers - no problem per metabox's instructions)

Oh, thank you all for such wonderful ideas and links. We have not made a decision yet, but at least we have some options now!