Elliptic Curves with Complex Multiplication  
   Defined over extensions of type (2,...,2). Tables by Joan-C. Lario.
   http://www-ma2.upc.es/~lario/ellipticm.htm

John Cremona's Elliptic Curve Data  
   Various data files in a standard format to make them easily readable by other programs, extending and correcting the tables in his book "Algorithms for Elliptic Curves".
   http://www.maths.nott.ac.uk/personal/jec/ftp/data/INDEX.html

Infinite Families of Elliptic Curves with Prescribed Torsion  
   Compiled by Andrej Dujella.
   http://www.math.hr/~duje/tors/generic.html

Rational Points on Elliptic Curves  
   A wide collection of known integer solutions to elliptic curves and their corresponding Diophantine equations, presented by Hisanori Mishima.
   http://www.asahi-net.or.jp/~KC2H-MSM/ec/eca1/index.htm

Siegel Forms  
   Coefficients of some Siegel automorphic forms, by Richard Borcherds.
   http://math.berkeley.edu/~reb/papers/siegel/

Drinfeld Modules  
   Complete tables of sign-normalized, rank one, Drinfeld modules on the elliptic curves over finite fields of order less than 16.
   http://www.math.umass.edu/~dhayes/dmods.html

Elliptic Curves with Unusual Torsion  
   Two tables: the smallest conductor observed for a given rank and torsion, and the smallest conductor observed among curves of rank zero with a given Sha and torsion. Maintained by Tom Womack.
   http://tom.womack.net/maths/torsion.htm

High Rank Elliptic Curves with Prescribed Torsion  
   The highest rank currently known for an elliptic curve over Q with each of the possible torsion groups. Compiled by Andrej Dujella.
   http://www.math.hr/~duje/tors/tors.html

Class Polynomials of CM-fields  
   Class polynomials of the principal orders up to discriminant -300000, giving values of the Weber invariants. By Annegret Weng.
   http://www.exp-math.uni-essen.de/zahlentheorie/classpol/class.html

Modular Forms Database  
   Tables computed by William Stein using HECKE, LiDIA, PARI and Magma.
   http://modular.fas.harvard.edu/Tables/

Best Known Conductors for Elliptic Curves of Given Rank  
   Up to rank 9, by Tom Womack.
   http://tom.womack.net/maths/conductors.htm

Modular Polynomials  
   Tables and Maple software for modular polynomials of composite level by Masanari Kida.
   http://matha.e-one.uec.ac.jp/~kida/modularpoly.html

Research Information - Larry Lehman  
   Includes a list of publications with abstracts, and tables of elliptic curves of small rank and various conductors.
   http://www1.mwc.edu/%7Ellehman/research.htm

310716 Elliptic Curves of Prime Conductor  
   The elliptic curves of prime conductor less than 10^8 found during computations performed at Fordham University during 1989 and 1990. Some additional materials are also given.
   http://www.oisinmc.com/math/310716/

Iwasawa Invariants of Elliptic Curves  
   For each curve (labelled as in Cremona) the mu and lambda-invariants are listed for the primes between 2 and 17. By Robert Pollack.
   http://abel.math.harvard.edu/~rpollack/Data/data.html

Mordell Curves  
   Minimal known positive and negative k for Mordell curves (y^2=x^3+k) of given rank, by Tom Womack.
   http://www.tom.womack.net/maths/mordellc.htm

Deformations of Maass Forms  
   Tabulated by Stefan Lemurell.
   http://www.math.chalmers.se/~sj/Maass/

Classical Modular Polynomials  
   Tables of modular polynomials Phi_l for prime l to 270, computed by Michael Rubinstein. Gzipped text and specially compressed formats.
   http://www.math.uwaterloo.ca/~mrubinst/modularpolynomials/phi_l.html