When you make a website, or design some logo, you will try to find good and free fonts for your using, while the best fonts are paid ones, there are excellent free fonts that might beat some of (not all) premium ones.
I like open-sans, because it is free, personal and commercial use allowed also it is available in google web fonts and has amazing readability,
another amazing, light and beautiful font, it is available in google fonts, and if you notice that google like this font, they used it for their headers in the Nexus 6 page!
it is amazing for design and web purposes.
is a basic sans-serif fonts, which can be used as main font in OS, it has great readability in small sizes ex. it is used in elementary OS Freya 3,
the famous adobe open-source font, it is suitable for web purposes.
is a very good font, it is very good in design things, it has difference from other fonts, but I wouldn’t recommend this for web purposes.
a very nice font which can be used for both web and design use, it has a unique characters shape, and really similar to the popular Promixa nova and Gotham,
this font is one of my favourite fonts, it is used in the text you are reading now, truely amazing and reliable font,