One way to get some extra IBU's out of you hops, and a subtle aroma to make its way into your final product, is to add them to your boil kettle during the sparge. As the wort runs from your mash into the kettle (first wort), it will start to isomerize the alpha acids in the hops to produce bitterness. Since first wort isn't yet boiling (and therefore not as volatile), it can also help contain some of the aromas from the hops that would otherwise be lost in a full boil. The aroma is softer and less pronounced than dry hopping, but it works to a small degree!