There are a few free alternatives here, but my tool of choice is TunerPro. It is free and the .xdf files are easy to modify and customise once they are set up.
I have posted a "how to" on Creating Tuner Pro xdf's which can be found here: Creating Tuner Pro maps for the Td5 ECU .
Since first posting this information I've made some changes to my XDF offer. I now give anyone who donates $5.00USD or more to the site download access to 2 zip archives containing XDF's for most NNN and MSB ECUs. These XDF's are updated with new information and table definitions every few months, and are now far more detailed than Td5MapEditor
For users who prefer Td5MapEditor, I follow the same map numbering convention for the basic maps so it should be easy to translate. For some modifications you will need a hex editor. As of mid-2017, the XDF's have begun including scalar definitions for ECU modules which I cannot reasonably support for those who choose to stick with Td5MapEditor.
Finally a logger of some kind is essential.While it's not ideal the Nanocom is currently the only game in town when it comes to logging to file.If there is sufficient interest there is potential for a barebones MicroSD datalogger to be made available. The additional data it logs is directly related to the core maps used in this method of tuning.
I've been using MegaLogViewer HD for a few years, and this is my log viewing tool of choice. A really nice feature of this app is the ability to create calculated fields. You can do things like create calculated fields for MAP and MAF Airmass based on the Nanocom log data. Once created these are available any time a log with the fields used in the calculations is loaded. It's a massive time saver!
There are versions for Windows, Mac and Linux. It is not free, however there is a time limited demo if you want to check it out.