Do you know which camera is good?

I would like to find a SLR camera that uses SD card, would you mind to give me some advice on which one is best with the budget of 300 usd?
Moreover, for small one, I am changing my Pentax optio S5i, which one should I change to? Thank you very much.

www.dpreview.com is the best site for camera reviews.

$300 for a DSLR is going to be quite a feat. I would look for a used on Ebay (Buyer Beware)

Instead I would suggest a fully manual Point and Shoot from Canon or Nikon.

The price range you are looking at should land you a camera in the 8MP range with decent optics out front.

Find the newest models from each of the manufactures and then review last year's model. The prices normally drop significantly after the new models hit the street.

But act fast.... sometimes they are hard to find!

FotoFletch is right.

The Pentax uses SD cards and the smallest DSLR uses that memory cards is the Nikon D40. That camera sells for under $500 for it and a 18-55mm lens.

You have two options ... look on craigslist in a city near you for a used one closer to your budget or save the additional money and buy a new D40

Sample listing in my area:
http://phoenix.craigslist.org/ele/638579...
http://phoenix.craigslist.org/pho/648415...

http://www.jdpower.com/electronics/ratin...

Or you can look here for good used DSLR's

http://www.bhphotovideo.com/bnh/controll...

While no used camera is listed at this time, they are listed from time to time.

Check KEH Camera Brokers They Are The World's Largest Used Camera Supplier. I Have Seen Used Pentax And Canon SLR's For $300-$400. I Have Been Very Pleased With My Purchases From Them.