First of all a link to Stephen G. Hartke's »A Survey of Free Math Fonts for TeX and LaTeX«, and Walter Schmidt's »Mathematikschriften für LaTeX« (in german).
Many fonts come with math support. If you haven't taken a look at those, do so. They can be found on the page with Fonts with math support.
The euler package provides some math support using the euler fonts.
\usepackage{euler}
or with one or more of the options
\usepackage[mathbf,mathcal,text-hat-accent]{euler}
The eulervm package provides some math support using the euler fonts too, but uses some enhanced virtual fonts.
\usepackage{eulervm}
or with one or more of the options
\usepackage[small,text-hat-accent,euler-digits,icomma,OT1,T1,LY1]{eulervm}
The sansmath package provides some math support for sans serif fonts.
\usepackage{sansmath}
\sansmath
or with one of the options
\usepackage[eulergreek,EULERGREEK]{sansmath}
\sansmath
The MnSymbol package provides math support for the Adobe MinionPro fonts, but may also work with other fonts. The MnSymbol package is not part of TeX Live, but can be found on CTAN at http://www.ctan.org/info?id=mnsymbol.
\usepackage{MnSymbol}
or with one of the options
\usepackage[mnsy,cmsy,abx]{MnSymbol}