Please nominate your favorite Scheme libraries

[lassik]

Here are some recommendations from @weinholt:

• (chibi match) - excellent pattern matching syntax. There are a few R6RS-adaptions here and there, but the original from foof is in Snow and Akku.
• struct-pack - tooting my own horn here, but this R6RS library implements pack/unpack for bytevectors. Similar libraries exist in Python and Perl.
• nanopass - a compiler framework
• packrat - a parser library
• r6rs-pffi - portable foreign-function interface
• SRFI 1, 13 and 115 for lists, strings, and regex.
• htmlprag, which is in a few places, e.g. wak-htmlprag - pragmatic HTML parser and emitter

[lassik]

r6rs-pffi added. Feel free to suggest/send PRs about other libraries.