Nikon D3100 video fps?

Can the Nikon D3100 shoot in 720/60fps

No the D3100 only shoots at these rates

640 x 424 (24p): 24 fps (23.976 fps)
1280 x 720 (25p): 25 fps
1280 x 720 (24p): 24 fps (23.976 fps)
1280 x 720 (30p): 30 fps (29.97 fps)
1920 x 1080 (24p): 24 fps (23.976 fps)

If you want to shoot at 60fps you would need a dedicated HD video camera and not a DSLR but I do believe that some of the higher end Canon DSLRs might be able to shoot at 60fps. Hope this helps.

Nope, only the T2i, T3i and higher Canon models do that.

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