All the tools I am using at the moment are free of charge. The one that comes to mind first is R. It’s a language for statistical computing which comes with a decent GUI. R comes with some time series support out of the box, but there are plenty of packages (R extensions are called packages) which provide powerful functionality. I remember using all of the following (in order of decreasing use):
The best part is that I don’t feel like I need any other language at this point! I have considered trying to speed up some R simulations by coding them in C++, but I can wait a few days for them to finish if necessary:).
For small scripts I use Python – it’s a great language which I discovered recently and I am trying to learn.
The other important part is data. My main source is Yahoo Finance. Let me first say, that in my opinion it’s one of the best sites on the Internet in terms of both design and content! It also has a lot of historical data. R comes with at least two interfaces to load historical data from Yahoo transparently, and so does most of other software I have used.
Another low cost data source is EODDATA. I have purchased access to some of their data.
And that’s all for tonite!