I'm a Logos man. Sure, there are other options out there (Accordance, Bible Works), but I enjoy Logos' original language tools, extensive and growing library, and how beautifully it works on my iPad.
They just released a new collection of quotes for preachers. Normally I'm not so interested in such collections since they are often a mixed bag of helpful/unhelpful selections. Sort of like getting a can of mixed nuts. The almonds, cashews, and spanish peanuts are gold, but then there's a bunch of blah in there as well. But in Logos' 1,500 Quotes for Preachers you get 300 Quotations from the Early Church, 300 Quotations from the Medieval Church, 300 Quotations from the Reformation, 300 Preachers from the Puritans, and 300 Quotations from the Modern Church. This gives you the words from more than one hundred authors and works, including Augustine of Hippo, John Chrysostom, Anselm of Canterbury, Thomas Aquinas, John Calvin, Ignatius of Loyola, Richard Baxter, John Bunyan, G. K. Chesterton, Charles Spurgeon, and more.
Not only is it all good stuff, each quote comes with an accompanying slide for use in preaching and teaching, and of course it's all searchable by theme, title, and affiliated Scriptures. But what makes it awesome is that everything links back to the original sources within Logos. Boom! Preachers need to do better than merely combing resources for a pithy quote. They should invest themselves in the original sources as much as possible, and this makes it easy to dig into the original material (immediately if you own it, or you can purchase to unlock).
Check it out. This is good stuff. 1,500 Quotations for Preachers, with Slides (5 vols.)