Making your own website or app is a great creative outlet. This is a continuously updated repository of free (or reasonably priced) resources for spicing up the UI/UX:

Illustrations

For those of us who are utterly not artistically inclined, jazz up landing pages and blog posts with these fantastic free illustration. Many of the images you see on this site are taken from these sites:

Icons & Glyphs

Pepper these through out to keep things interesting:

Colour schemes

For those of us who know what looks good but can’t come up with it on our own, colour palette generators and inspirations are essential: