Just joined the noun project and they have some great icons! The only problem is that anytime I try to resize the icons to make them smaller (eg 64x64) they seem to get a bit fuzzy. Doesn't matter if I resize the png or svg file format. I export the files to png and use them for a website.
Assuming you are using Illustrator, download the SVG version, which is a vector format and can be used to generate a smooth PNG at any size you need.
Open and clean up the SVG file, then do a 'Save for Web' and type '64' in the 'Image size → Width' field and make sure 'Clip to Artboard' is not checked and PNG-24 is selected above.
To ensure even better smoothness, export a larger PNG, i.e. 128x128px, and scale this down to 50% in your CSS code.
This should probably also work via Photoshop using a similar routine.