What is the cheapest nikon dslr with HD video?

You can also give me canon names but first nikon.

Nikon D3100
Canon T3
Canon T1i

Right now probably the Nikon D90 ($900, body only) or the D5100 ($850 with 18-55 mm lens)

The D90 only shoots HD video. The D5100 shoots both HD and Full HD video

The D90 is more robust and can use legacy Nikkor AF lenses as well as the ultra fast auto-focus AF-S lenses

The D5100 uses AF-S lenses only if you want to use the auto-focus feature.

Nikon dSLR's at this time are the only ones that can auto-focus in the video mode

Nikon D3100
Canon EOS T3
Canon EOS T1i

Here's a DSLR Buying Guide - http://www.the-dslr-photographer.com/2009/11/which-dslr-to-buy/