I don't think there is, certainly not that I've ever seen on a D3000/3100/3200/5000/5100/5200
You can use the focal length markings on your lens to get a fairly good estimate of where you're at, but I understand sometimes you want to know the exact value. For example, when I was debating between a 35mm & 50mm lens, I was guesstimating if my lens was at those lengths when using my 18-55mm - I wasn't far off usually, but there were a few 49mm and 51mm & 52mm shots.
The only way I have found so far though, is when I attach my SB-700 flash. Instantly on the flash's LCD I can see the focal length of my lens, and it changes in RT as I zoom in/out