Here are some of my favorite applications for Android. I own an HTC Evo 4G and love to make it easy to use and look nice. These all work together to make a great system even better:
Launcher Pro: A home screen replacement for Android that allows you to add multiple docks to the bottom of your screen. You can have up to three sets of five icons to hold your favorite apps. Launcher pro has icons for many popular applications, to provide a more uniform look. You can customize the amount of pages that can be swiped through on your Home Screen, you can change the background color of the dock, there are tons of options. In addition, you can add swipe gestures for each icon to open different applications or shortcuts (you can set it up to display a preview of messages when you swipe over the messaging icon or you can have it open a folder of your favorite applications when you swipe over the launcher icon. Probably the best application in the Marketplace so far. Buy the Pro version to get HTC sense like widgets.
Itching Thumb: This application allows you to use Palm Pre-like gestures to close and open apps. It runs on top of the home screen, so you can use Launcher Pro as the main home screen and use it as an addition, only opening when you double tap the home button.
Gesture Search: Google's application, Gesture Search, allows you to open applications with gestures, similar to Itching Thumb. You draw letters on the screen and Gesture Search will search certain files on your phone. You can set it up for music, applications, calendar information, and contacts, or a combination of them. It is a quick and easy way to open any application on your phone.
Appbrain Marketplace: Appbrain is an enhanced version of the Tradiotional Android Marketplace. Instead of showing featured applications at random, it uses your existing applications to show you suggestions. In addition, Appbrain allows you to sort applications by most popular this week, today, and more. It is a great way to discover applications that typically are harder to find in the Marketplace. Also, Appbrain allows you to sync your application list online so you can remotely add or delete applications and see when they are updated. If your phone is lost or stolen, you can reinstall all of your applications at once from appbrain. It is an amazing way to find and manage applications.
Tasker: Tasker allows you to set customizable actions based on a variety of events happening (essentially a blocky way to program with a nice interface). I have it configured to go into silent mode whenever I am in class based on time and date, then turn the sound back on after class. Also, the phone can occasionally turn on WiFi to see what networks are nearby, or use GPS to add a location. When I am within my WiFi range in my room, the phone enables WiFi and connects. When I leave range, it turns off. Tasker could tell you to pick up groceries when you drive near the supermarket as well. Its possibilities are almost limitless. It is well worth the $6