Daily UI is a 100 day UI challenge put forward by dailyui.co. Designers receive a daily email with a design prompt every day except weekends. Prompts read along the lines of "design a music UI" or "design an app icon"...etc.
It allows new designers to keep practicing to improve their skills while allowing seasoned designers to flex their creative muscle by giving them the freedom to let loose without any constrictions besides the prompt provided by Daily UI.
Here are a few of my favorite designs. Follow me @don_kiros for more Daily UIs.