VideoDog is a command line tool to grab frames from a Video4linux-compliant device. It can export a file in raw, PNM, or JPG formats. It can also do loop capture using multiple buffers, or just be used to set/retrieve device data or scripts. It presents a programming interface for implementing image transformations and effects. There are some examples in the source code. No external libraries are required.
Tunix is a set of tools used to generate small bootable Linux images. It can be used to learn how to roll your own distribution, or to port embedded systems. The basic release uses busybox and has a kernel with netfilter-enabled modules. A uclibc iptables binary is included, so you can roll your small firewall from a floppy.