zdic.net

This site have probably been mentioned before, but I only really discovered it yesterday.

http://www.zdic.net/

You do need to be able to read a bit or have annotator tool installed to make good use of it, but it has some some excellent features.

You can look up characters by radical or pinyin and just give audio pronunciation for individual characters.

It also has an idiom database and an excellent appendix of useful information like measurement units, countries, capitals, populations etc, it even has a periodic table.