Choosin my first DSLR, CANON, NIKON OR SONY?

Well, my uncle has a nikon D90 and he always let me take it to events and take some photos, I've learn a lot of photography and now I need my own and first DSLR, the options with the money I have right now are: CANON REBEL XS/1000D, NIKON D3000, SONY ALPHA 230

I'd go with the Nikon. Second choice would be Canon.
Both are great.

Get the nikon, the least horrible of the three and you can borrow lenses from your uncle.

You should buy this new one model

My opinion is nikon d3100

The D3100 is an entry level digital-SLR camera equipped with a new DX-format CMOS image sensor with an effective pixel count of 14.2-million pixels and the new image-processing engine, EXPEED 2, both developed by Nikon, that enables the capture of high-definition images with superior image quality.

Notable Features:-
Compact and lightweight - Easy operation and take-anywhere portability

Continuous 3 fps shooting - Catch the decisive moment

Eye-Fi support - Transfer photos and movies wirelessly

New shutter mechanism - Quiet shooting, even with Live View

11-point AF system - Quick, accurate autofocus ready for the decisive moment