Using a Canon EX flash unit with an articulating bracket and a diffuser is a great way to go when lighting macros. I prefer the 550EX or 580EX because it is easier to use these on manual than the 420EX but, I don't know about the manual capability of the 430EX.
I learned this set up from Dr. Deepak Rao, a physician and a great macro photographer from Bangalore, India. Deepak often posts on the macro forum of digital photography review and I communicated with him regarding his excellent macro images and he told me how his outfit is set up. I no longer have the link to Deepak's macro galleries but, here are a few links to some images that he created.
Weekly macro/close-up thread for 2 December 07 [Page 3]: Canon SLR Lens Talk Forum: Digital Photography Review
http://www.pbase.com/dprchallenges/macro24_vibrant
ShutterFreeze :: Not a soothing macro
I use a Siegelite flash bracket. I don't believe that this model is produced anymore but, it is often available from eBay, usually at under twenty dollars.
The small softbox is a Lumiquest which I have had for years and years. It could be fabricated out of some cardboard or foamboard or diffusion material. I have seen Chinese knockoffs on eBay for about twenty dollars:
Velcro Flash Diffuser for Canon 580EX 550EX 430EX 420EX - eBay (item 190230674017 end time Jun-25-08 04:48:15 PDT)
You would of course need a Canon (or third party) off camera sync coed to set up an outfit like this.
I would imagine that you could substitute a Sunpak 383 or a Vivitar 385HV for the Canon flashes but, the exposure might be a little tricky.