Most if not all of the above, also this Behringer with sliders: http://www.behringer.com/EN/Products/BCF2000.aspx

Novation makes some very interesting controllers:
the SL MkII http://www.novationmusic.com/products/midi_controllers/sl_mkii
and the same thing without keyboard and X/Z pad, the Zero: http://www.novationmusic.com/products/midi_controllers/zero_sl_mk_ii

Novation support can help you if you ask specific questions via e-mail, I have done so and they were very helpful and straightforward.

Keep in mind that all of the above (as well as what others posted) are geared towards controlling computer based DAWs, synths etc. Verify that they can do what you want beforehand. Also make sure that the arranger or whatever you want to control with them CAN accept those kind of messages via midi coming from one of these controllers.

On the cheap side, if there is a PC available, maybe the Korg Nanocontrol can do it http://www.korg.com/product.aspx?&pd=415 (Pc is needed because this has only USB midi). you can use more than one of them if you want, for double the controllers.

edit: didn't see that Lee had already listed the Novation controllers. Anyway that makes two of us.

What exactly are you thinking of controlling? is it an arranger?

[This message has been edited by trident (edited 12-07-2010).]