Sites

The Riemann Hypothesis (Popularity: )
http://www.claymath.org/millennium/Riemann_Hypothesis/
Article by Enrico Bombieri (PDF) and video by Jeff Vaaler (.ram) from the Clay Mathematics Institute.

Riemann's Hypothesis (Popularity: )
http://www.users.globalnet.co.uk/~perry/maths/riemannshypothesis/riemannshypothesis.htm
A beginners guide by Jon Perry.

Riemann's Zeta function (Popularity: )
http://numbers.computation.free.fr/Constants/Miscellaneous/zeta.html
Notes by Xavier Gourdon and Pascal Sebah.

Louis de Branges de Bourcia (Popularity: )
http://www.math.purdue.edu/~branges/
Purdue University. Proposed solution for the Riemann Hypothesis (pdf format).

Analytic Number Theory (Popularity: )
http://www.math.harvard.edu/~elkies/M259.98/index.html
Lecture Notes by Noam Elkies, Harvard, 1998.

Vinogradov's Three Primes Theorem (Popularity: )
http://www.dpmms.cam.ac.uk/~wtg10/
Lecture notes on the home page of Timothy Gowers (DVI format).

Riemann's Paper (Popularity: )
http://www.maths.tcd.ie/pub/HistMath/People/Riemann/Zeta/
"Ueber die Anzahl der Primzahlen unter einer gegebenen Grösse" and in translation.

Easy Proof of Riemann's Hypothesis (Popularity: )
http://www.coolissues.com/mathematics/Zeta/zeta.htm
Generalisations of the zeta function might provide a proof of Riemann's hypothesis.

Zeta Values on the Web (Popularity: )
http://wain.mi.ras.ru/zw/
A bibliography compiled by Wadim Zudilin on values of the zeta function with links to those papers available on-line.

Irrationality and Transcendence (Popularity: )
http://web.maths.unsw.edu.au/~angell/5535/
Lecture notes (PS) by David Angell, NSW.

The Mark of Zeta (Popularity: )
http://www.maa.org/mathland/mathtrek_6_21_99.html
A MathTrek article by Ivars Peterson.

The Music of the Primes (Popularity: )
http://www.dpmms.cam.ac.uk/~dusautoy/2soft/music.htm
A popular article by Marcus du Sautoy on the Riemann Hypothesis; Science Spectra, Issue 11.

Ten Trillion Zeta Zeros (Popularity: )
http://www.maa.org/editorial/mathgames/mathgames_10_18_04.html
A Math Games article by Ed Pegg junior on Xavier Gourdon's computations.

Computation of Zeros of the Zeta Function (Popularity: )
http://numbers.computation.free.fr/Constants/Miscellaneous/zetazeroscompute.html
Verification of RH up to the 10^13-th zero, with details of the computations and further results, by Xavier Gourdon with the help of Patrick Demichel.

Zetagrid (Popularity: )
http://www.zetagrid.net/
Numerical verification of the Riemann Hypothesis by a collaborative computing effort, with downloadable software.

The Riemann Hypothesis (Popularity: )
http://aimath.org/WWN/rh/
Some of the conjectures and open problems concerning RH, compiled by the AIM.

The Riemann Hypothesis (Popularity: )
http://www.utm.edu/research/primes/notes/rh.html
A prime pages article by Chris K. Caldwell.

The Riemann Hypothesis (Popularity: )
http://www.mathpuzzle.com/riemann.html
A short article with some grahpical and numerical evidence in the critical strip.

The Riemann Hypothesis (Popularity: )
http://users.forthnet.gr/ath/kimon/Riemann/Riemann.htm
A short article by Kimon Spiliopoulos.

Proof of Riemann's Hypothesis (Popularity: )
http://www.coolissues.com/mathematics/Riemann/riemann.htm
A claimed proof of Riemann's Hypothesis.