Before you start working on a look, you should ask yourself a couple of questions (that you already know the answer to, but would help as guides for what you want to do). First of all, who are you developing/designing for? My guess is tech savvy users that need effectiveness. You probably don't need something amazingly beautiful, but you do need something easy to use.
Some things you might consider from a design point of view are:
Highlighting elements depending on their importance. You can do this by using color, for example. A nice program that has some ready palettes is Kuler. You could pick one, and experiment with the colors. Also, font size and spacing can help differentiate elements a lot.
Aiming for consistency (but not uniformity!). Once you have a style, you could ask yourself: Do all fonts look like they belong to the same family? (in your case, you have times and Arial, so the answer is no!), do same text sizes represent the same hierarchy?, do all widgets have the same width, margins, padding, etc? Your elements belong to different categories, thus they should look different.
Making it 'pretty' by using support elements. Would you enjoy working x n of hours with your app? What can you do to make it friendlier? Can you add icons so people can identify easily which button does what? Right now all I see are (pixellated) search icons everywhere. Maybe you could choose one graphic element for each widget (sites like iconfinder have cc icons).
Once you are happy with what you see, you can try with some tests (5 second tests are great for this, or you could ask your friends and colleagues for their opinion) and see how people react to it. Or you could upload it somewhere (like Forrst) and ask for opinions.