Customize your LINUX I/O

BusyBox

http://busybox.net/

DHCP util:
http://isc.org/software/dhcp/411/download/dhcp-411targz
JTAG,Serial port,RJ45
http://www.mips.com/products/processors/hard-ip-cores/4kec-hard-ip-cores/

http://www.mindspeed.com/web/download/download.jsp?docId=28723

VoIP Client

http://www.asterisk.org/
http://sourceforge.net/projects/openh323/

DNS and DHCP Server

http://www.thekelleys.org.uk/dnsmasq/doc.html

VLAN

http://www.candelatech.com/~greear/vlan.html

HotPlug

http://isteve.bofh.cz/~isteve/hotplug2/

NTPClient

http://doolittle.icarus.com/ntpclient/

Build HTTP Client for your Linux

https://openwrt.org/

Lightweight C library

http://www.uclibc.org/

http://www.fefe.de/dietlibc/

Kernel Trap

http://kerneltrap.org/site

Micro C-Real Time kernel
http://www.micrium.com/page/products/rtos/os-ii