I'd recommend a Sigma 530DG Super. It's about the same price as the Canon 430 (around $200) but has more power and more features that you'll grow into.
The Canon is easier to swivel / tilt (a single button vs separate buttons) but the extra power is always welcome.
If you can stretch the budget, the 580ex is never a bad choice. (It's about $400 though).
If you're familiar with running manual mode, you can't beat the Vivitar 285HV for value. It's $90 brand new, and has an automatic mode that you match up to your ISO and f-stop. We used them for years with the older Canons because the original E-TTL was so unpredictable.
Hope this helps!
Shan