Thank you Adelle...Proofhub ( proofhub.com) is actually really good, not only for timesheets but for complete project management.
Nodoubt, Basecamp is good but it lacks important features like time tracking, private messages and integration with google. Have you tried proofhub? Features like time tracking, casper (hidden) mode, to-do's, discussions make it awesome. So, you don't miss anything.
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.
Basecamp sets the standard for ease of use and also importantly in data sharing with other applications. It would even be better if they told developers when they change their API!
I've been using Wrike for a month now and it's really been a terrific tool.