libraries: improve content

Addresses #293.

Author: agarwal

site/learn/libraries.md

@@ -1,16 +1,38 @@
 <!-- ((! set title Libraries !)) ((! set learn !)) -->
 
 # Libraries
-* OcamlPro's [official OPAM repository](http://opam.ocamlpro.com/pkg/)
- is likely to be the most comprehensive list of OCaml libraries.
-* The [Caml Hump](http://caml.inria.fr//cgi-bin/hump.en.cgi) is a
- comprehensive directory of tools, libraries, code samples and tips.
-* The [OCaml dedicated forge](http://forge.ocamlcore.org/) contains
- more than 250 projects.
-* Many libraries are also developed on
- [GitHub](https://github.com/languages/OCaml).
-* Some libraries are shared on
- [Bitbucket](https://bitbucket.org/repo/all/relevance?name=ocaml&language=ocaml).
+
+There are thousands of OCaml libraries available. Here is a list of
+the most popular sites where you can find them.
+
+* [Official OPAM repository](http://opam.ocaml.org) is the first place
+  to check. The most high quality and most widely used libraries are
+  provided as OPAM packages.
+
+* [GitHub](https://github.com/languages/OCaml) is an extremely popular
+  code hosting site and very widely used amongst OCaml
+  programmers. Click the link to find OCaml projects. Remember that
+  many of these libraries are provided as OPAM packages, so you'll
+  have already found them in OPAM. However, there are many more
+  libraries here that people haven't pushed to OPAM for one reason or
+  another.
+
+* [OCaml Forge](http://forge.ocamlcore.org/) is a code hosting site
+  dedicated to OCaml projects. Hundreds of libraries are hosted
+  here. Like GitHub, many of these libraries are in OPAM, but you'll
+  possibly find many here that aren't.
+
+* [Bitbucket](https://bitbucket.org/repo/all/relevance?name=ocaml&language=ocaml)
+  is yet another code hosting site. It is far less used amongst OCaml
+  programmers, but click the link to find those that are.
+
 * [OASIS-DB](http://oasis.ocamlcore.org/dev/home) is a collection of
- released OCaml packages.
+  released OCaml packages. It is an alternative packaging system to
+  obtain OCaml libraries.
 
+* [Caml Hump](http://caml.inria.fr/cgi-bin/hump.en.cgi) is now
+ deprecated. For many years, it was the definitive source to search
+ for OCaml libraries. It is hosted on the old caml.inria.fr, which is
+ being retained because there are many links on the internet pointing
+ to this site, but is no longer maintained. You should not rely on it
+ for up-to-date information.