Hi Mike, It looks like you are really enjoying your photography by trying sports and landscapes, so now the decision is what's next macro or telephoto.  Macro is a very specialized lens, but can give you hours of enjoyment and great images, the world up-close makes for very interesting photographs, you take the person looking at your images into a whole new world.  Now with telephoto, it can be very useful in many ways, sports, landscape nature, people.  So long and short I would say telephoto first, you can always rent a macro, and don't forget extension tubes and your 50mm make for great close-ups too.  Hope this helps, Heather.

I have been into photography for two years now and I'm shooting all kinds of different things, sports, landscapes, snapshots etc.  I'm shooting with a Canon 40D and have the following lenses: Sigma 70-200 2.8, Sigma 17-70 2.8-4.5, Canon 50mm.  I feel at times like I want a longer zoom and at times wish I had a macro lens...Any thoughts on a specific next step?  I'm torn...  Thanks.