Coda is great, easy to use and has a very nice look to it, however it is only available on a MAC and does require you pay about 100 dollars for it.
Eclipse is available on just about every platform and can handle just about every language. Eclipse is also free to use, however it can be a bit complex for beginners.
Today however I have found a third choice that shows some promise. It’s called Code Any Where. It stores all your code in the cloud so it is available everywhere, and you can create a multitude of different test/development systems to try your code out on. This is great for testing. Although it does have some paid options, you can use most options for free. They are also developing some apps for mobile devices to access your code, however the reviews on these have not been the best.
So while I still encourage everyone to use CODA, Code Any Where shows a lot of promise and may be worth checking out.