For those of you who are interested in seeing what spreads are currently being offered or bid, the CBOE has a link to the COB, or Complex order book. This will list all spreads listed at the CBOE that are currently able to be bought/sold electronically (If a broker is holding the order it may not be listed) http://www.cboe.com/cob/cob.aspx Very helpful if you are considering legging a spread. What you want may already be there.
That is really interesting that the CBOE is doing that. Amazing what demutualization has wrought, for the better, imo.
IF you use TOS you can see what's going on in ISE's COB. (see screenshot) I guess the only exchange that's left is PHLX. However I once had a butterfly spread rejected when I routed to it to the PHLX. The TOS rep I called up couldn't figure out why either and put me on hold. He called up the exchange itself and it turns out they only accept two legs at time. So much for executing butterflies on philly.