The LANDIS-II repositories are moving to GitHub (thanks Marc!) because Google is shutting down their current location. I was using TortoiseSVN with google code so am learning TortoiseGit. I have been using GitHub's Windows client for another project and it has worked OK but seems to lack some of the more complex functions. So far, however, it appears that the two clients can be installed side-by-side with no consequences.
I used this document as a guide for installing TortoiseGit. Note in the pre-requisites that you should install Git for Windows before installing TortoiseGit.
I used this document as a introductory guide for using TortoiseGit. Note that after I followed the instructions in the aforementioned document, all of the installation steps had been completed. You do need to create public and private SSH keys for GitHub. You can save the public key to your user account on the GitHub web page. Save the private key to your local computer. When you clone your first repository, check the "Load Putty Key" box to supply the path to your private key for TortoiseSVN.
To CLONE a local copy of a repository, you will need the repository url. This can be found online on the right-hand side of a repository's web page. This document provides additional information about repository urls.
Saving your changes in TortoiseGit is a 2-step process. First you COMMIT your changes to your local copy. Second, you can SYNC your changes with the remote repository in GitHub. GitHub will ask you for your user name and password every time you do a sync. You can cache this information in TortoiseGit for each repository using the procedures in this document.