The idea that everyone has to be busy all the time is a dangerous one. I tell my teams "Any time you are doing something to keep everyone busy, you are on the wrong track. Stop and think about what you're doing." Keeping everyone busy on scheduled tasks will always lead to more handoffs and you'll have no buffers.
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 Instead, have a "shadow backlog" of work you need to do to be a better team. Include efforts to streamline the build, to automate tests, to learn better ways to use your configuration management tools, etc.  This is work that has value but no hard deadline. It's the perfect buffer. You don't get velocity points for it, but doing these things should raise your velocity for user-requested stories. Having a technical discussion about which things should be done is a good way to build buy-in and commitment to it, as well as giving technical leadership a way to shine.
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 * Nancy Van Schooenderwoert, on [[http://tech.groups.yahoo.com/group/leandevelopment/message/2470|leandevelopment@yahoogroups]]

See also, ''Slack: Getting Past Burnout, Busywork, and the Myth of Total Efficiency'' (ISBN:0767907698) by Tom !DeMarco