When I first started raising baby birds, I found these websites extremely useful. As I have continued to raise baby birds, I still use much of their advice, which has help shaped the instructions on this website. Most of the information on sites about raising wild baby birds will be the same, but many of these sites go into more detail about the species and weight development of baby birds. This website simplifies the information and puts it into steps for all ages to use.
2nd chance is a remarkably detailed and useful guide to raising baby birds by Dr. Ron Hines DVM PhD. He goes into much more detail than this site provides and I highly recommend reading it over.
Starling Talk is a similarly thorough and helpful source for orphaned bird care information. While the site caters to starlings and sparrows, the care is very similar to other perching birds.