For $300, you have a few choices. Haha, and only $300? I thought your name was "Deep Pocket". Haha just messing. Anyway, There are a couple flashes out there that would fulfill your needs depending on what you want.
I will start off with a pretty decent flash, one from Opteka with E-TTL II, so it'll be a simple flash to use. I've had this flash before and it was above decent. For about a hundred bucks, it's a pretty good deal and it's like a less expensive 430EX II.
Here: http://opteka.com …eosdigitalandfilmslr.aspx
Next, we have the Canon Speedlite 430EX II, it's a great flash that I had for about five months, I used it mostly in manual mode, but I also used it in E-TTL mode while on top of my camera. It's about $200 without any diffuser. Well, there's also the 430EX Classic which is cheaper, it may me $200, and the 430EX II may be a bit more, and some differences between the two is that the 430EX II has improved recycling times, and also the 430EX II has a metal hotshoe mount which is really good since a lot of people have had problems with broken flash shoes.
Last, but definitely not least, are the older flashes. There is the 420EX, an the 550EX. These were flashes built over five years ago. These "EX" models will also give you TTL functionality, which will be a great addition since you were not able to use the 540EZ with E-TTL. The 420EX goes for about $150 around Craigslist and POTN, and the 550EX goes for what.. around 200-300 dollars around eBay and POTN?
Take a look around, read some things here and there. Good luck!