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.
If there are any objects using the current cell, those will be shown in black. Validation formula references and conditional formatting formula references are shown in black as well.
The Visualize option shows improved trace precedents arrows:
The Object Reference Enables you to see what your cells are used by objects on your sheets, such as Pivot tables, Charts and etcetera.
And here is a screenshot of the tool after detecting circular references:
RefTreeAnalyser integrates nicely with Excel 2007, 2010 and 2013:
and of course also supports Excel 2003.