Why, don't you like the Canon ones?  Metz makes some good shoe mount
uints.

Here is a list of the flash guns I am aware of that are E-TTL-compa-
tible (sort off),

In addition to Canon's own models, I've listed some third party flash
guns claimed by their manufacturer to be "Canon digital" compatible.
These third party guns use reverse engineered interfaces for E-TTL
compatibility.  The Sigma 500 DG Super has a fair reputation for E-TTL
compatibility, the Metz models have received more mixed reviews in
this area, but make up for this by having an excellent auto mode.  The
Sunpak. Promaster and Quantum are new entries, and I've haven't seen
any reports on their compatibility yet.

The Sigma and all the Canons except the 220 EX and 380 EX can be used
in a infrared wireless (w/l) master/slave setup (the 420 EX as slave
only) and are compatible with the wireless transmitter ST-E2.

----------------------------------------------------------------------
     Model                 GN   Notes
----------------------------------------------------------------------
  1. Canon 220 EX         (22)  No tilt/swivel
  2. Canon 380 EX         (33)  No swivel (discontinued 2001)
  3  Sunpak PZ40X         (40)  Rev. eng E-TTL.  Also power ratio.
  4. Promaster 7500DX     (42)  Rev. eng E-TTL.  Also auto.
  5. Canon 420 EX         (42)  W/l slave.
  6. Metz 44 AF-4C        (44)  Rev. eng E-TTL.  Also auto.
  7. Quantum Qflash T4d   (49)  Rev. eng E-TTL.  Also power ratio.
  8. Sigma 500 DG Super   (50)  W/l master + slave. Rev. eng.
  9. Metz 54 MZ-4C        (54)  Rev. eng E-TTL.  Also auto.
 10. Canon 550 EX         (55)  W/l master + slave
 11. Canon 580 EX         (58)  W/l master + slave
----------------------------------------------------------------------
Models are sorted by maximum guide number (in meters, for ISO 100).
For technical details, see the manufacturers' specification sheets.

Alternatively, for variable power output, you may buy a non E-TTL
«auto» flashgun (like the Vivitar 283, GN 37).  This will work fine
on all Canon's digicams.  You set up the camera in aperture priority
mode, set the aperture you use on the flash, and let the flashgun
control the exposure.

If you don't want to spend the $180 a Speedlite 420EX will cost
you, a Vivitar 283 cost only about $67.  I would not recommend
to get a unit with less power than the Vivitar (GN 120ft/37m)
if you want an useable bounce.

A good tutorial on using flash is on:
http://www.camerahobby.com/Ebook-FlashTechnical_Chapter9Sub.htm