Suggestions for subeqn

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

Package autobreak: Simple line breaking of long formulae
Package abraces: Asymmetric over-/underbraces in maths
Package eqnarray: More generalised equation arrays with numbering
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 cases: Numbered cases environment
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 subeqnarray: Equation array with sub 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
Package bussproofs: Proof trees in the style of the sequent calculus
Package halloweenmath: Scary and creepy math symbols with AMS-LaTeX integration
Package luamathalign: More flexible alignment in amsmath environments
Package theorem: Manipulate theorem environments
Package amscls: AMS document classes for LaTeX