Depends on your level of adaptation. Novices generally tend to be stronger 48-72 hours after a given workout, if the workout is properly programmed to elicit the adaptation. Intermediates tend to need about a week of correctly programmed exercises to cause a strength adaptation. Advanced or competitive lifters typically need anywhere from a few weeks to a few months to add strength.
The best book I know of on this subject is Practical Programming by Rippetoe & Kilgore