I have for many years been breeding parrots and raising them both by hand and in the nest. I started by comparing the weight and growth rate of my hand-reared babies with those being reared by the parents and experimented with feeding formulas until I arrived at one which gave me similar results. This was before the advent of commercially prepared formulas. I still use my own formula for the first few days of rearing the babies, if you would like the recipe, please click on the 'Food' link below. Thereafter, I use 'Kaytee Exact' or 'Pretty Bird', but there are plenty of other makes that will give you good results.
It was difficult knowing what weight a baby should be at any given stage of development and how much food to feed it at that weight. In case others have the same worries hand rearing parrots, I thought I would copy my rearing sheets omitting personal details as not all these sheets relate to my own birds. See the links above for various species.
Parrot breeding information
I do not normally recommend particular sites, I like to leave you to do your own exploring. However, there is one site that you may find interesting if you have a pet parrot - http://www.birdtricks.com