I would first recommend you get the AMD 2500+ Mobility Chip over the Barton.
If you ever want to overclock, that chip has an unlocked multipler which will allow you to overclock without any problems.
As for motherboards:
ASUS A7N8X-E Deluxe $105
ABIT NF7-S $105
ALBATRON KX18D PRO II $92
are top to bottom recommendations imo.