For changing your home screen look, I think the best option is GOLauncher. It's a great launcher with TONS of sweet customization options. The same dev team produces a ton of useful widgets and themes that go along with the launcher.
For a widget app, I would HIGHLY recomment Fancy Widget Pro. Get the paid version. I have both FWP and Beautiful Widgets and I think FWP is better, hands down. It has VERY good Sense clock knockoffs and overall just seems a little more slick than BW.
If you want to take the next step with theming then you need to check out MIUI. Theming on the MIUI rom is unparalleled.