Suggestions for eqnarray

The following packages have something in common with the package eqnarray. The packages are ordered in decreasing similarity.

Package cases: Numbered cases environment
Package subeqnarray: Equation array with sub numbering
Package systeme: Format systems of equations
Package spalign: Typeset matrices and arrays with spaces and semicolons as delimiters
Package witharrows: Aligned math environments with arrows for comments
Package eqnalign: Make eqnarray behave like align
Package odesandpdes: Optimizing workflow involving odes and pdes
Package autobreak: Simple line breaking of long formulae
Package abraces: Asymmetric over-/underbraces in maths
Package thmtools: Extensions to theorem environments
Package newproof: Make commands to define proofs
Package resizegather: Automatically resize overly large equations
Package blkarray: Extended array and tabular
Package cancel: Place lines through maths formulae
Package dotseqn: Flush left equations with dotted leaders to the numbers
Package empheq: EMPHasizing EQuations
Package ebproof: Formal proofs in the style of sequent calculus
Package fitch: LaTeX macros for Fitch-style natural deduction
Package nccmath: Extended mathematics capabilities
Package oubraces: Braces over and under a formula
Package prftree: Macros for building proof trees
Package polynom: Macros for manipulating polynomials
Package subeqn: Package for subequation numbering
Package thmbox: Decorate theorem statements
Package ytableau: Many-featured Young tableaux and Young diagrams
Package breqn: Automatic line breaking of displayed equations
Package longdivision: Typesets long division
Package shadethm: Theorem environments that are shaded
Package ntheorem: Enhanced theorem environment
Package kbordermatrix: LaTeX version of \bordermatrix
Package nicefrac: Typeset in-line fractions in a nice way