Lpc2000

> Is there any implementation of ZigBee on LPC2100 and some (so far
> "rare") IEEE 802.15.4 PHY/MAC available?

Be careful about what you can "any implementation of ZigBee" because you
neet to figure out what functionality you need (device, coordinator, and
so on).  As for 802.15.4, try the Chipcon CC2420 is a rather popular
choice and they have a freely-available (subject to license acceptance,
IIRC) MAC for it.

--
Paul Curtis, Rowley Associates Ltd  http://www.rowley.co.uk
CrossWorks for MSP430, ARM, AVR and now MAXQ processors