NetworkWorld has a nice article on starting a SOA initiative.  NetworkWorld's last piece of advice might be the most important: do not try the "big bang" approach.  It is not recommended by vendors and will cost you a lot of money.  In addition, the importantce of a good SOA architect should be emphasized.  KPI highly recommends organizations to spend the $150/hr on a good SOA architect.   Given the amount of money companies are losing on SOA, a good SOA architect at $150/hr is cheap (and has a much higher ROI than spending $150/hr on two SOA folks).