The Chinese Biographical Database is an ambitious project which seeks “to include all significant biographical material from China’s historical record and to make the contents available free of charge, without restriction, for academic use.” A collaboration between researchers at Harvard, Academia Sinica, and Peking University, it has for several years been one of the more reliable online reference works for Chinese history. Searches can be made in English or Chinese, though the results are unwieldy and would likely confuse a non-specialist.
This database has recently been made available as a downloadable Mac dictionary. I have not yet had a chance to try it out, but I’m optimistic that its interface will be friendlier.
Below is a screenshot of what the interface looks like.