Yes MarginalRevolution is about economics, but most of all it is about ideas. The blog Crooked Timber and legal scholar Lawrence Solum both offer fascinating takes on which contemporary philosophers will still be read decades or centuries from now.
My personal nomination is Derek Parfit. I think his Reasons and Persons will provide a source of conundrums for undergraduates, graduate students, and researchers for many years to come. Parfit is not just a philosopher, he is also a social choice theorist. He challenges our very notions about what it means to say that one outcome is better than another. He ponders how we should think about the timing of costs and benefits, whether personal identity matters for just distribution (who cares what you got yesterday?), how we should regard moral theories that are self-defeating when implemented, and how we should value future generations.