While I would agree in general with the replies, I would advise:

Home Depot now carries a complete line of Cat5 cables and
jacks.
run PVC conduit to each outlet location.
use a string in each to pull cables. As you pull each
run, pull another string for future runs.
Plan for a central location with a 10/100 ethernet switch.

Don't worry about "too short" runs. Basically, any "run" from
the switch or hub will be fine, if not longer than 100 meters.

FWIW. - fb