Method to iterate through SharePoint SPSite collection to check to 
see if a feature (featureGuid) exists.  If found, method returns true.

 
 
 private bool FeatureExists(SPSite siteCollection, Guid featureGuid) { 
    bool found = false; 
    foreach (SPFeature feature in siteCollection.Features) { 
    if (feature.DefinitionId == featureGuid) {
      found = true; 
      break;
    }
  }
 
 return found;
}
 

Cool eh?