Akku.scm is a language package manager for R6RS Scheme.
Industria is a collection of portable R6RS Scheme libraries for cryptography. It implements low-level algorithms like AES, RSA, DSA, ECDSA, etc and high-level protocols such as OpenPGP, Off-The-Record messaging, DNS and Secure Shell (SSH).
machine-code is a set of tools for working with machine code (disassemblers, an x86 assembler, ELF format, stuff like that).
r6lint is a linter for R6RS Scheme. The idea is to help the programmer write better code by checking the code on the fly in the editor.
Zabavno is an x86 emulator in R6RS Scheme.
More projects at GitHub.