My 2.5 year old has recently developed what can be best described as a stutter.
It only seems to occur with us, and mostly when asking a question ("Wh, wh, wh, wh, what's that Daddy?). It's especially pronounced if he is tired.
It doesn't concern us greatly yet, he's happy and sociable. In fact it doesn't tend to occur around strangers.
Update: He's started to garble whole sentences recently, again mostly when he's tired, but he's also started getting noticeably frustrated.
His vocabulary is very wide and still growing quickly - if anything, it feels like his mouth can't keep up with this brain!
Is this similar to others experiences - how did you approach it? Should we ignore it (for now) and make no special effort, or would simple speech therapies help?
Update - 2.5 years later: It was just a phase, passed in a few months. He's near top of his class for reading, writing and spelling (phonetically or not).
As suggested in the great answers (and common with so many aspects of kids growing up), keep an eye on it to make sure it's not an early warning - but don't panic :)