If there's a library you like, and you'd like to see it available to download and install via the standard Quicklisp dist, here's what to do.
First, make sure the license terms of the code allow for its redistribution. I can't add things with restrictive licenses or with licenses that are missing or unclear.
Second, make sure it works on more than just one implementation of Common Lisp. Quicklisp is for portable libraries. (In the future, I hope to make it easy to create separate new dists specifically for implementation-specific code, but even then, the main Quicklisp dist will be for portable libraries.)
As a side-effect of how I build and test the dist, it must also work on SBCL on Linux/AMD64. That means, unfortunately, that a great portable library that works on three different Windows CL implementations, but not on Linux, cannot be added. I hope to fix this limitation in the future.
Third, make sure the library has certain ASDF system definition metadata: :license, :author, and :description. It also should have a README file in some form or another. A note about the README: it should give at least short overview of what the library is for. "The Foo library is an implementation of Ruby's Snorfle in Common Lisp" is not a good overview; give me an idea of what it actually does, instead, e.g. "The Foo library fetches and parses movie showtime information." It's good to also provide information about how to report bugs and how to contact the author.
Fourth, make sure it builds with ASDF, rather than an external-to-Lisp build mechanism. I can't add libraries that require special configuration or action outside of ASDF. For example, if you have to edit a source file to configure library or resource directories before building, I can't add it to Quicklisp. If the library can be loaded with just (asdf:load-system ...), it's good.
Finally, let me know about it. I prefer to track requests via github's issue system, but you can also send me an email as well. It suffices to write something like "Please add the foo library, which is available from http://www.example.com/foo.tgz. The homepage is http://www.example.com/foo/."
It's important to note that I don't consider a library's quality or purpose when adding it to Quicklisp. It doesn't matter if you're submitting your own library. If you want it added, and it fits the above criteria, I will almost certainly add it.
There are a few exceptions: projects that require complicated or obscure foreign libraries, projects that can only be downloaded via some ad-laden link system like SourceForge, projects that use CVS, and anything else that makes it difficult for me to fetch or build the project.
When you open a github issue for a library, I'll occasionally update the issue's status. I will add issue comments if I have any problems building, or if any required bit of information (license, ASDF metadata, README) is missing.
Barring any problems, when the github issue for a library is closed, the latest Quicklisp dist has been released and it includes the new library. (Sometimes I mess this up, so if it seems like the library is still missing after a dist update, feel free to get in touch.)
How about updates? Many libraries do not need any extra work to get updated regularly in Quicklisp. For example, if a library can be downloaded from an URL like "http://example.com/cool-project/cool-project-latest.tgz", Quicklisp will detect when a new file is posted. For libraries downloaded from version control systems like git, updates are also automatically fetched. Only when a library uses a fixed URL per version is it necessary to open a github issue for updates.
Quicklisp dist updates happen about once per month. If the library is updated upstream, those updates will only be reflected after the next Quicklisp dist update. Each dist update freezes the state of the Quicklisp library "world" until the next monthly update.
If you'd like to see the process in action, watch the quicklisp-projects issue page for a month to see how things typically work.
If you have any questions about the process, feel free to get in touch.
Update: See also Some problems when adding libraries to Quicklisp, which explains how the above process can go wrong sometimes.