For the most part, I don't want to mess with my kids when they're "in the zone," but I have tried a few little tricks lately that I've learned from the ever-inspiring Christie Burnett from Childhood 101.
This post on story cards prompted me to add pictures to the play area. I gathered up some random pictures from various sources, like magazines, old photo albums, pieces from a memory game or whatever you have laying around. We use the pictures to tell a story. Of course, my two year old can't exactly come up with a complete narrative at this point, but I ask some guiding questions and we chat together about what the characters are doing; making up basic stories about the characters as we go. This isn't much different than the way we read books--lots of talking about the pictures as we read the text. The cards are novel though, so it's just one more fun way to get him communicating and thinking about stories.
I also love the idea of setting up play scenes. -Gathering materials that your child would find interesting, and setting them up in an inviting way. Yesterday, I put out some trucks, a few playdough "rocks," plus a tiny playdough road for my son to discover. An hour later he was still building roads and making tracks, and his big brother even had time to join the fun and build a few freeways before kindergarten. My mom has always been a master at this. Before the kids come home from school or visit her house, she often sets up a special block tower with a few favorite Lego guys inside, or lays out a pile of interesting kitchen utensils or unique selection of art materials. It's an invitation to play that encourages kids to think about using different materials, and it inspires them to use their own toys in different ways.
You can learn about play scenes and much more in the fabulous Play, Grow, Learn e-zine. (It's my new favorite download! A must read for anyone working with kids!) And if you want to know more about Christie, catch this interview on another awesome blog, Not Just Cute.
Oh, and if you'd like more ideas for encouraging play, be sure to bookmark and browse the Playopedia! You'll find tons of unique play ideas in a well-organized catalog. (My Shadow Stories are included--Yay!)