46fc74b06b034d47c8ec5dbf81e7e7ec 500x646 - Outlook Email Sidebar

I love the fonts, colours and layouts for this outlook mockup. If only more email clients looked this good. Designer: Frantisek Kusovsky Source: Dribbble  

Outlook Email Sidebar

142285669449065072 wBBIHZ1B c 500x286 - Sleek UI Elements

A clean no-nonsense UI with a good colour palette. Designer: Matthew Daniels Source: Design Kindle

Sleek UI Elements

261631059574161391 HHeBpSmL c 500x367 - Cloudy UI Kit

This is a great clean UI kit which is available to download from 365psd. Designer: Sebastien Gabriel Source: 365 PSD  

Cloudy UI Kit

Pandora UI Free Full s 500x361 - Pandora Full UI

This is an excellent free UI for designers which could be used for a range of projects. Designer: Designmodo Source: Designmodo

Pandora Full UI

web elements psd 1 by lewisbell d3cfp5g 500x286 - Web Elements

Source: http://lewisbell.deviantart.com/art/Web-Elements-PSD-1-202286356

Web Elements

material ui kit 500x378 - Material UI Kit by UI8

This is a great UI kit based on the Android Material UI theme guidelines. If you are designing a new android app this would be great. Source: UI8

Material UI Kit by UI8

Productivity Platform

Trying to get the design for a web app right is hard work. This design for a todo list app is really good. I particularly like the dark color scheme he is used. Source: Deviant Art

Productivity Platform by skirilov