Zurb Foundation - comprehensive alternative, includes lots of templates
Skeleton - minimal option
Initialzr - includes a basic responsive template by default, but can also integrate with Bootstrap (mainly for integrating HTML5 Boilerplate with Bootstrap)
Flat UI Kit - based on Bootstrap, but lots of styles and colours in the 'flat' design.
Gumby - Responsive grid, uses Sass by default
Inuit - Based on Sass and uses OOCSS
Buscando framework CSS ligeros encontré y recomiendo mirar Pure(jquery) y Picnic.
Resumen tras googlear:
http://www.hongkiat.com/blog/bootstrap-alternatives/ skeleton cardinalcss concisecss powertocss furtive basscss mueller tuktuk base toast
http://stackoverflow.com/questions/9212536/alternatives-to-twitter-bootstrap Blueprint.css
Zurb Foundation - comprehensive alternative, includes lots of templates Skeleton - minimal option Initialzr - includes a basic responsive template by default, but can also integrate with Bootstrap (mainly for integrating HTML5 Boilerplate with Bootstrap) Flat UI Kit - based on Bootstrap, but lots of styles and colours in the 'flat' design. Gumby - Responsive grid, uses Sass by default Inuit - Based on Sass and uses OOCSS
http://www.monolinea.com/css-frameworks-comparison/ ⋅⋅⋅ middleweights Gumby Groundwork ⋅⋅⋅ lightweights Pure Base KubeCSS