I just got the Canon Rebel 300D Digital SLR camera. What brand of Compact Flash card is the best one to use?

I would like a 4G card. which is the best one to use?

Really, I dont like using cards that big. Im pretty happy using a 1gb card and having a few of them. Reality, you arent going to take that many pictures when you go out and having 2 1GB cards is fine.
Now...here is why. Say you fill up a 4GB card and now want to edit them on a computer. Those 1000s of pictures are going to take a long time to load on your computer. Also, not all the pictures you take are going to be that great. With larger cards you are going to tend to fill up those cards with every single picture. Instead of sitting down and erasing all the bad pictures, you are going to end up putting all those on your computer. That many pictures are going to fill up your computer really quick.
Basically, ive just come to the realization that smaller cards are easier to deal with on a daily basis.

gee dunno?

Really any major brand will work fine.

Don't spend a lot of extra money on a card with a higher than 50x rating ... so far none of the current DSLR's have the electronics to utilize them.

Currently 4GB cards can be found on sale for under $50, 2GB under $20

Some samples of brands to consider:
SanDisk
pqi
A Data
Transcend
Kingston
Lexar
Kodak
And of course more

I use a mix of 2GB and 4GB cards on assignment.

Believe it or not, all of the compact flash cards on the market today are manufactured by only two companies: Lexar and SanDisk. Those two companies, however, only put their own name on one line of product. Needless to say, they reserve their best technology and research findings for their own brandname. My advice: recycle those crummy cards the camera came with and stick to the source; you'll pay a little more, but you won't have a card fry up your camera and void the warranty. SanDisk or Lexar should have a 4 GB or even an 8 GB at Costco for pretty cheap.

Brand don't matter too much. Get one with at least 40X speed.