Agile software development processes by any definition encourage the in- and-out team communication via various practices from pair-programming to informative workspace to retrospectives. With the respect to all the usual practices there is one more often underestimated way of getting the in-team feedback - the hallway testing. The term Hallway Usability Test coined by Joel Spolsky stands for "grabbing the next person that passes by in the hallway and forcing them to try to use the code you just wrote. If you do this to five people, you will learn 95% of what there is to learn about usability problems in your code."
While it is a perfect way to do quick usability testing (especially if the team works in individual offices or cubicles, rather than in a war room), it can be used for fast getting a peer for the micro-brainstorming, peer review or just chatting about the architecture. And if you develop software for the mobile devices, sometimes there is no need even to invite the peer to your place.
This practice looks simple, is simple, but also is effective. Though to make it working, you might need to encourage people to come to the hallway more often. For example, by placing there couple of sofas and a coffee machine.