How can I group and output a collection by a Reference Field and also Alpha like you see on these two pages?
http://madisoncountybarassoc.org/members/ (sorted and ground alpha)
http://madisoncountybarassoc.org/lawyers-by-practice/ (grouped by specialty)
Do I need to setup a collection for each Letter and Reference Field?
In the first example, the number of letters in the alphabet is > than the allowed number of collections per page. So that poses an issue. As a workaround you could break up the list over multiple pages.
In the second, you would do better with SEO, to limit the collection list to a practice area per page.
Another concept would be to make a page for each (assuming you don’t hit your page limit) and then use the dropdown on the master page to pull the relative pages content in via Ajax.