Below is a screenshot of the RefTreeAnalyser, showing both dependents and precedents of a cell.
Note that it shows the value in each cell next to its address and also highlights references which evaluate to an error in red automatically.
The Visualize option shows improved trace precedents arrows:
And here is a screenshot of the tool after detecting circular references:
RefTreeAnalyser integrates nicely with Excel 2007, 2010 and 2013: