A Forrester study from 2009 found 1 in 3 software development teams are using some form of agile development models including Extreme Programming, Crystal Clear, Lean and Scrum. Scrum is the most popular, but it's not as if every development team is doing it exactly the same way.
Scrum focuses on rapid deployment of software via 2 week sprints, a lack of top-down hierarchy and getting customers involved from the onset. The point is to make software that is useful and turns development investment in to a working product quickly and accurately. There are some basic rules: you need a team of about 10 people with a sprint leader, you need a focus on business results and everyone on the team should be in the same room or as close as possible to keep the agility and nimbleness only a few steps away. You also need to be ok with rolling product out quickly so testing and implementation need to be built in to the code very early on. If something doesn't work, quick, daily review meetings should help realign the components of the team in to something more useful or that functionality can be moved to a later version in another sprint.
Mathew Schwartz, who writes for Dice's career news site, had this to say about Scrum in his excellent article on the trend in software development in Scrum:
"Benefits to this "controlled burst" approach include delivering more relevant software, lowering business risk and creating more satisfied coders. "Every two weeks we get the chance to improve what we're doing, and we can do it with the customer," says Alan Atlas, a certified ScrumMaster trainer and agile development coach with Rally Software in Boulder, Colo. "No longer do we have to spend two years to see if something we build will work.""
Software developers not familiar with agile development processes need to get familiar as the trend continues to gain popularity and find effectiveness in business.