Web source: Nucleotides and Nucleic Acids

A superb animated primer on DNA, genes and heredity
http://vector.cshl.org/dnaftb/

A copy of the classic Watson and Crick paper
http://biocrs.biomed.brown.edu/Books/Chapters/Ch 8/DH-Paper.html

An interview with Francis Crick
http://www.accessexcellence.org/AE/AEC/CC/crick.html

DNA Chime tutorial
http://www.mc.maricopa.edu/users/ayres/org_molecules/chime1.htm

More nucleotides in 3D
http://info.bio.cmu.edu/Courses/BiochemMols/BuildBlocks/Nucs.html

Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid

http://en.wikipedia.org/wiki/Molecular_structure_of_Nucleic_Acids

Nucleotides in 3D
http://www.nyu.edu/pages/mathmol/library/dna/

Nucleic Acid Structure

http://dl.clackamas.edu/ch106-09/nucleic.htm

Nucleic Acid Databases

http://ndbserver.rutgers.edu/

Ooops! Left and Right Handed DNA
http://www.lecb.ncifcrf.gov/~toms/LeftHanded.DNA.html

Profile of Oswald Avery
http://www.profiles.nlm.nih.gov/CC/

The Structure of Nucleic Acids

http://www.vivo.colostate.edu/hbooks/genetics/biotech/basics/nastruct.html

The Structure of Nucleic Acids (Animation)

http://www.moleculesinmotion.com/NucAcids/title.html