desicreative.com

Just random tweeting may get your precious message lost. So whats the best time to tweet? How do you find that out?

I use Tweriod.
Tweriod is a free twitter tool that helps you make the most of Twitter by letting you know the best time to tweet.
The free analysis will analyze up to 1000 of your followers. Tweriod is not affiliated with Twitter.

Another nice tool is FollowerWonk
Followerwonk helps you explore and grow your social graph.

Dig deeper into Twitter analytics: Who are your followers? Where are they located? When do they tweet?
Find and connect with new influencers in your niche.
Use super-actionable visualizations to compare your social graph to others.
Easily share your reports with the world.