Suggestions for mathtools

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

Package mhsetup: The mathtools setup function
Package empheq: EMPHasizing EQuations
Package upgreek: Upright Greek letters
Package centernot: Centred \not command
Package eqnlines: Single- and multiline equations
Package delimset: Typeset and declare sets of delimiters with convenient size control
Package extpfeil: Extensible arrows in mathematics
Package extarrows: Extra Arrows beyond those provided in amsmath
Package gensymb: Generic symbols for both text and math mode
Package iwonamath: LaTeX support for scaled Iwona math fonts
Package letterswitharrows: Draw arrows over math letters
Package mattens: Matrices/tensor typesetting
Package mathpartir: Typesetting sequences of math formulas, e.g. type inference rules
Package mathbbol: Use the bbold fonts in mathematics
Package sansmath: Maths in a sans font
Package steinmetz: Print Steinmetz notation
Package trfsigns: Typeset transform signs
Package underoverlap: Position decorations over and under expressions
Package xfrac: Split-level fractions
Package accents: Multiple mathematical accents
Package euler: Use AMS Euler fonts for math
Package faktor: Typeset quotient structures with LaTeX
Package turnstile: Typeset the (logic) turnstile notation
Package tensor: Typeset tensors
Package mathalpha: General package for loading maths alphabets in LaTeX
Package tensind: Typeset tensors
Package aligned-overset: Fix alignment at \overset or \underset
Package setouterhbox: Set hbox in outer horizontal mode
Package pxgreeks: Shape selection for PX fonts Greek letters
Package vector: LaTeX macros for vectors
Package mathcomp: Text symbols in maths mode