For historical reasons, the following names come into play for each of the two packages.
scikit-learn - the name of the package as listed on the project's website.
scikit_learn - the name of the package to download and install.
sklearn - the name of the module to import.
scikits.learn - the name of the older version of the package, visible with enpkg and in Canopy's Package Manager. Do not install this, as it may cause conflicts. If you do install it, you can simply uninstall it using the same method that you used to install it.
scikit-image - the name of the package as listed on the project's website.
scikits.image - the name of the package to download and install. This is an older name still being used by Canopy's Package Manager to search/install/remove the package. This is different from the official PyPI repo used by pip / easy_install, which uses scikit-image. We are working on updating this in our repo to avoid future confusion.
skimage - the name of the module to import.