Describe the updated Busybox variants in a little more detail

busybox/content.md

@@ -1,6 +1,6 @@
 # What is BusyBox? The Swiss Army Knife of Embedded Linux
 
-At about 2.5 Mb in size, [BusyBox](http://www.busybox.net/) is a very good ingredient to craft space-efficient distributions.
+Coming in somewhere between 1 and 5 Mb in on-disk size (depending on the variant), [BusyBox](http://www.busybox.net/) is a very good ingredient to craft space-efficient distributions.
 
 BusyBox combines tiny versions of many common UNIX utilities into a single small executable. It provides replacements for most of the utilities you usually find in GNU fileutils, shellutils, etc. The utilities in BusyBox generally have fewer options than their full-featured GNU cousins; however, the options that are included provide the expected functionality and behave very much like their GNU counterparts. BusyBox provides a fairly complete environment for any small or embedded system.
 
@@ -26,10 +26,14 @@ COPY ./my-static-binary /my-static-binary
 CMD ["/my-static-binary"]
 ```
 
-This `Dockerfile` will allow you to create a minimal image for your statically compiled binary. You will have to compile the binary in some other place like another container.
+This `Dockerfile` will allow you to create a minimal image for your statically compiled binary. You will have to compile the binary in some other place like another container. For a simpler alternative that's similarly tiny but easier to extend, [see `alpine`](https://hub.docker.com/_/alpine/).
 
-## More about this image
+## Image Variants
 
-The tags of this image are built using two different methods. The `ubuntu` tags are using the `busybox-static` package from Ubuntu, adding a few support files so that it works in Docker. It's super fast to build (a minute or even less). The `buildroot` tags are going the long way: they use buildroot to craft a whole filesystem, with busybox but also all required libraries and other support files. It has a stronger guarantee of "this will work". It is also smaller because it's using uclibc, however it takes hours to build.
+This image contains BusyBox built against various "libc" variants (for a comparison of "libc" variants, [Eta Labs has a very nice chart](http://www.etalabs.net/compare_libcs.html) which lists many similarities and differences).
 
-Having two totally different builders means that if one of the goes belly up, we can always fall-back on the other since this image is used in much of build testing of `docker` itself.
+-	`busybox:glibc`: [glibc from Debian](https://packages.debian.org/jessie/libc6) (which is then included in the image)
+-	`busybox:musl`: [musl from Alpine](https://pkgs.alpinelinux.org/package/main/x86_64/musl) (statically compiled)
+-	`busybox:uclibc`: [uClibc](https://uclibc.org) via [Buildroot](https://buildroot.org) (statically compiled)
+
+For more information about the specific particulars of the build process for each variant, see `Dockerfile.builder` in the same directory as each variant's `Dockerfile` (see links above).