The Japanese writing system has a long and deep history, tracing back to the scratching on Oracle Bones in ancient China. This depth of history thus carries a huge weight of etymology behind it. This etymology is not just frivolous either. The old forms of chinese are used in Chop Seals which are effectively signatures of legal documents.
The difficult thing with the etymology of a given Kanji is actually quite problematic. When Han'zi characters were imported to japan, they were (generally) imported as their "traditional" version. During the communist revolution in China, the government simplified a great number of characters. Thus, there are currently two versions of a given Chinese character. For example, the character for "see" is 見 in Traditional Chinese, and Japanese, but 见 in Simplified Chinese. To make it even more confusing, there are a few characters of exclusively Japanese origin (called Kokuji). Finally, the Japanese went through their own simplification process.
What this boils down to, is that if you are wanting to study the Etymology of a Kanji character, you might have a couple of places to look. The first step is to take a peak at this great Chinese etymology database put together by Richard Sears. You can feed it a simplified or traditional chinese character, and it will come back with results. The only time that it doesn't come up with any results, is when you try and input a kokuji, or even just a Traditional Chinese character that the Japanese simplified (if that is the case, you can search for the kanji you are looking for at the link I just provided).
On a completely different angle, the writing of Kanji has progressed in a different direction, which is to say, calligraphy. I'll be talking about that more in another post, but I thought I would mention 2 great calligraphic dictionaries I have found:
Both dictionaries are on Mainland China, which means they are exclusively simplified Chinese. This means that if you want to look up a traditional chinese character, you need to find its simplified equivalent. This isn't too hard, because Thats where Richard Sears saves the day again. It provides a good amount of information on any Chinese character you feed it. Simplified or Traditional.
Even if you are not studying Japanese (or Chinese!) you should go have a look at these sites, some of them have quite beautiful imagery, and it it is quite interesting to see the etymology of a few different characters. If you need some example characters, you can use these (you'll just have to copy/paste them):