I loved the Zafira workshop I attended 1.5 years ago. The had one instructor on a stage in front, and then had another one at floor level on the side or in the back for when you turn around, and then a third roving instructor. Worked like a charm.

Just like library presentations, bonus points go to handouts-- the choreography written out, some sort of historical background, translation of the song being used, and maybe a glossary of terms. Also, people generally make an extra buck or two if they have CDs of the choreography music to sell at the end of the workshop.

Something that's not for everyone is videos. Personally, I've loved watching them in the past-- either seeing a professional presentation of the same choreography, or in the case of a workshop with Aegela on Turkish v. Egyptian dance, a classic example of the genre. I think the key is just to make sure that the clips are fairly short so that no one loses their warmed-upedness.

My favourite workshops are those that deal with a specialized theme, especially nitty-gritty technique of a particular style/region with all of the history thrown in. "How to do your own choreography", "Breaking down and learning zyll patterns", etc. Most of the dancers I used to study with were especially interested in workshops that dealt with costuming and make-up, culminating in professional photos.