Link building - promote science blog

I have a physics related blog / information website and would like to get some good quality links in. I'm not looking for anything automated but a small number of REAL (google friendly) links. I would like guest blog posts etc and / or permanent links on sidebars / footers of relevant websites.

If you can help with this please let me know roughly how many links you think you can get, and on what kind of sites, and what the likely overall cost would be.

Thanks