Asana is fantastic tool. But we will wait while they add time tracking in asana. For now we use excellent time tracking system in ProofHub (proofhub.com), its project management abilities are a bit simpler than in asana, but time tracking functionality is really good.
Thank you Adelle...Proofhub ( proofhub.com) is actually really good, not only for timesheets but for complete project management.