1. A computer implemented method of managing human resources comprising: maintaining and periodically updating, on at least one memory device of a computer system of a company, a record of human resource supplies, said human resource supplies comprising individual human resources available from internal and external supply sources with respect to said company, said record of said human resource supplies comprising a list of different skills of each of said individual human resources and an indication of availability of each of said individual human resources; providing a business strategy comprising offerings of said company and profitability and revenue targets for said offerings; based on said business strategy and on said record of human resource supplies, periodically developing, by a first processor of said computer system, a set of rules providing guidelines for obtaining said human resource supplies from said internal and external supply sources and for assigning said individual human resources to satisfy said offerings, wherein said developing of said set of rules comprises: prioritizing said internal and external supply sources; and setting at least one of target supply bench levels, target investment levels for training, and target investment levels for acquisition; based on said set of rules and said record of human resource supplies, periodically developing, by a second processor of said computer system, a first-level plan specifying which of said internal and external supply sources should be used, over a specified first time period, to satisfy ongoing demands, future demands and possible demands, wherein said first-level plan is periodically developed at shorter intervals than said set of rules, and wherein said developing of said first-level plan comprises: developing a list of engagements for said offerings during said specified first period of time, said list of engagements comprising ongoing engagements generating said ongoing demands, future engagements generating said future demands and possible engagements generating said possible demands; based on said list of engagements, developing a demands list comprising a list of any skills required to satisfy each of said ongoing demands, said future demands and said possible demands; and based on said set of rules and on said record of human resource supplies, indicating, in said first level plan, skill types and numbers thereof from said demands list which are to be sourced through currently available internal supplies, through supplies available by acquisition, through supplies available by skill development, and through external supplies; based on said first-level plan, on said demands list, on said record of human resource supplies and on said set of rules, periodically developing, by a third processor of said computer system, a second-level plan, said second-level plan recommending assignment of a specific individual human resource to satisfy a specific demand within a specified second time period, wherein said second-level plan is periodically developed at shorter intervals than said first-level plan, wherein said specified second period of time is within said specified first period of time, wherein said second-level plan comprises a short-term plan as compared to said first-level plan, and wherein said developing of said second-level plan comprises: selecting, from said demands list, said specific demand, wherein said specific demand requires satisfaction within said specified second time period; selecting, from said record of human resource supplies, said specific individual human resource, wherein said specific individual human resource has a required skill to satisfy said specific demand and can be assigned based on said set of rules and said first-level plan; and recommending, in said second-level plan, assignment of said specific individual human resource to satisfy said specific demand after said developing of said second level plan, evaluating, by a fourth processor of said computer system, said second level plan, said evaluating comprising: determining a current availability of said at least one specific individual human resource; and reviewing pricing information to determine whether a cost of assigning said specific individual human resource to satisfy said specific demand is within previously established cost guidelines; when said specific individual human resource is currently available and when said cost of assigning said specific individual human resource to satisfy said specific demand is within said previously established cost guidelines, assigning, by said fourth processor, said specific individual human resource to satisfy said specific demand; and, when said specific individual human resource is not currently available or when said cost of assigning said specific individual human resource is not within said previously established cost guidelines, assigning, by said fourth processor, a different specific individual human resource from said record of human resource supplies to satisfy said specific demand based on said set of rules, on current availability of said different specific individual, on said pricing information, and on said set of rules.