Free SMS <-> IM/Email gateways?

I have a phone that runs Windows Mobile (6), with an unlimited data plan (so I am capable of sending/receiving email, and installing IM clients if I want).  As such, SMS seems a bit like overkill, and I have not subscribed to an SMS service on my phone.

I would like to be able to find a free gateway between SMS and IM (and/or email) in order to be able to send/receive messages to folks who are limited to SMS, or come up with a solution I could deploy myself that would do the same thing.

My resources are as follows:
Cell phone w/ WM6 (previously mentioned)
DSL connection at home, with DynDNS autoupdates
Local webserver (linux)
Local mailserver (linux)
Asterisk server with Linksys SPA3102 (for POTS integration )
Local voice/data modem

http://www.textmarks.com/ seems like one way to allow folks with nothing but SMS to contact the rest of the world (and I could see how to easily adapt that into an email or IM gateway so I could receive such messages on my phone).

I don't have any great ideas for outbound - maybe some sort of solution using TAP through Asterisk (and/or the modem).  Sending to short codes (and common short codes) would be icing on the cake, but I'm not expecting any miracles.

Any ideas?

Cheers,
-Jon