Vacuum Diagrams and Manifold Time
science fiction by Stephen Baxter; a good interpretation of current physics knowledge
The Life of the Cosmos
by L. Smolin 1997 Oxford University Press
Time Without End: Physics and Biology in an Open Universe
by Freeman Dyson 1979, Rev. Mod. Phys.51, 447. Speculations by a noted physicist
Searching for Interstellar Communications
1959, G. Cocconi and P. Morrison, Nature 184, 844-846
Intelligent Life in the Universe
by I.S. Shklovskii and Carl Sagan, 1966, Dell Publishing Co., New York
The Galactic Club - Intelligent Life in Outer Space
by Ronald N. Bracewell, 1974, (reprint of Stanford Alumni Association publication) W. H. Freeman & Co.,San Francisco
Life in the Universe
edited by John Billingham, 1981, MIT Press, Cambridge. Proceedings of a 1979 conference at NASA/Ames.
Interstellar Migration and the Human Experience
by B.R. Finney and E. M. Jones, 1984, Univ. of California Press, Berkeley. The Fermi story is found here, also Dave Criswell's and other futuristic schemes.
Search for Extraterrestrial Intelligence @ Home
The home of the largest distributed computing project on Earth. Many details on radio SETI techniques and results at /about_seti/ under this URL.