What you need:
OpenWrt can be installed on many different router-hardware.
See here for a list of supported devices.

What you get:
Compared to other router system-software, OpenWrt by default is a
very slim system. You can think of “minimalistic”=”more
secure”.

Almost everything you’ll ever need can be simply installed as
packages or compiled by yourself. (e.g. a webserver/VoIP-proxy
a.s.o.)

For GUI-enthusiasts the white-russian-release also offers the
possibility to update, and configure your router via web-interface,
although most of you people will be happy to have ssh-access and
therefore full control over you linux-routerdevice.

Getting even more:
Most of the listed hardware devices, can use external or internal
memory-sticks, sd-cards or at least nfs or samba shares, to install
more software or hold more data accessible from your router.

How you can help:
Back to my initial thought for this blogentry.
As your router is usually up 24/7, and most people have flatrates,
there’s a great possibility to support the TOR network by
installing a tor-server on your router and use it(or not) from
within your LAN by accessing privoxy on your router to browse the
web anonymously for example.

What is TOR:
TOR (The Onion Router network) is a concept to tunnel
networktraffic through multiple other nodes before connecting to
the final destination node. That way it will be harder for
evesdroppers to trace your origin IP-address, and for hosters more
safe to offer content without the danger of being shutdown when a
server-ip might get blocked by someone.

Further you can provide access to the whole internet, dedicated
services or even dedicated addresses through your own TOR
server.
If you don’t want others to use your router to access the internet,
you can just contribute as a tunnel-peer for other
TOR-servers.

Where to get:
All required packages for OpenWrt-capable routers can be found here
and a precompiled privoxy-package here.

I’m addicted:
Of course you can do even more crazy stuff with OpenWrt see
here.

Peace !