Note: This is pretty old now, and I'm no longer maintaining it. But I'll leave it up as it still has a few users.
Gmittook is a popular, free, lightweight, cross-platform Twitter client. It can also be set up as an email notification client with an inbuilt email viewer.
New: Fixed issue to work with Twitter API update
This all-in-one tool makes it easy to reply to your friends and share information between Twitter from a single desktop window.
Or you can use it just as a Twitter client on it's own.
This new version allows you to set scheduled text tweets.
View tweet locations on map:
It also includes a tweet mapping viewer, search for any topic (eg. snow, rain) and see where recent tweets have been sent from. This uses the geolocation data included with some tweets.
This version also allows you to view current trends based on location.
It includes a mail notification service which works with many webmail services (gmail etc) and a email manager.
You may need to install Java first. You can get the latest version here.
Download the version you require here:
Windows (2k/XP/Vista/7/8): Download
Map geo-location tweet searching
Fixed - direct message, mentions indicators.
Couple of bugs fixed.
No need to restart after setting changes.
View trends by location.