A quick look at cleaning downspouts showed that there are various ways to clean them and more interestingly, some ways to keep them clean. Most rain gutter guards fail to keep debris out of the gutter and out of the downspout. We showed one interesting set of products.
The attachment between the downspout and the rain gutter in the Easy-Flow system is deep and beveled to help any leaves flow downward without clogging. Then, there is a separator system on the bottom that kicks the leaves forward and lets the water go on down. This is an especially interesting system when your downspouts go into the foundation footing drain as you certainly don't want to plug that up with leaves. Made by Easy-Clean.