There are plenty. It depends what you want to pay. The behringer http://www.behringer.com/DCX2496/index.cfm?lang=ENG

is a very popular unit amongst DIY types. Be aware it spit's out pro levels.

There are significantly more expensive units from dbx, klark technik, bss.

Another alternative is the expensive, but more consumer (rather than pro) oriented DEQX http://www.deqx.com/product.html

To really make a good job of this, rather than to merely screw around, you need very good measurements of the speaker(s)/drive units in question.. The tools to make those measurements can cost more than the crossovers...

It is a good idea to be fully familiar with Vance Dickason's "Loudspeaker Design Cookbook" (at a minimum) before you get started on whatever it is you have in mind...