Many of the resources below are free or very low cost, and are sure to be useful to a lot of designers and developers out there.
As always, if we've missed something you think should have been included, please let us know in the comments. And if you have an app or other resource you'd like to see included next month, tweet it to @cameron_chapman for consideration.
Spectrum is an OS X app that makes it easy for you to create color schemes intuitively. It uses built-in harmony rules for composing color schemes, as well as a color picker, a tool to make schemes from images, and built-in library, and more.
Sellbox lets you sell your digital files via your Dropbox account. Receive funds through PayPal, and only pay Sellbox a 5% cut without any upfront fees.
Pocket is an official Read it Later app that makes it easy to save articles, videos, or any other content for later. It works from your browser, email, and more than 300 apps, including Twitter, Pulse, Flipboard, and more.
Wireframe.cc is a minimalist wireframing app that's both a pleasure to use and beautiful to look at. Controls are simple and intuitive, and the end result is quite attractive.
Manymo is an Android emulator that starts quickly and runs smoothly right in your browser, letting you test your Android apps. It supports more than 42 screen sizes and OS versions.
Photo Raster is an advanced online photo editor that includes tools for painting, filters, adjustments, layer editing and masks, and more.
Bitrix24 makes it possible to create your own social intranet in just minutes. There's a free account that supports up to 12 users and 5GB of files, while paid accounts add more users, more features, and more storage space.
Solidify is a new prototyping app from Zurb that lets you create clickable prototypes from wireframes, mockups, or even sketches. Plans start at just $19/month.
IconBench lets you customize a set of more than 700 icons. You can set things like opacity, drop shadow, inner shadow, gradient, and more, and then pick the icons you want.
rwdgrid is a responsive grid system based on 960.gs. It has different grid systems for 1200px, 960px, and 720px displays, as well as mobile screens.
Onlytasks is a new task management app for OS X and iOS that makes it easy to organize your tasks efficiently. It even synchronizes with Evernote!
WP Teacher is a new plugin for educators that lets them integrate course content into their WP site. It supports two post types (assignments and events), widgets for assignment lists & event lists, and more.
SimplyTestable is an automated front-end web testing app that allows for one-click testing of your entire site. It'll validate your HTML markup, give you an overview report of your site's successes and failures, a detailed per-URL error report, and more.
Stride is a sales management app that includes tools to track, manage, and collaborate on new business. It includes real-time collaboration tools to help your whole team work on deals, as well as useful metrics you actually care about.
JS Library Boilerplate
Fbootstrapp is a toolkit for building Facebook iFrame apps in both relevant sizes. It's based on Bootstrap and built with Less, but styled for Facebook.
Brunch is an assembler for HTML5 applications. It can be used with any framework, library, programming language, stylesheet, templating language, or backend technology.
Deployd makes it easy to build APIs for web and mobile apps quickly. There's no boilerplate or configuration, unlike traditional backends.
Viewport Resizer is a responsive design testing bookmarklet. All you have to do is go to the page you want to test, click the bookmarklet, and then view it in all kinds of screen resolutions.
Iconify is a portfolio site platform that lets you create a responsive portfolio viewable on any device, complete with your contact information. It also includes tools for sharing via social media, and it creates a downloadable mobile app version of your portfolio.
Simple Grid is a responsive, lightweight grid. It's 1140px wide with twelve columns, but easily adapts to any size layout.
One% CSS Grid
One% CSS Grid is a 12-column fluid grid system for building responsive layouts. It has two starting options, for screens of 1280px or 1024px wide, and uses a percentage-based grid system to perfectly adapt to any screen.
Yeoman is a robust set of tools and libraries, along with a workflow, for creating compelling, beautiful web apps. It includes thorough documentation, as well as a getting started guide.
Emmet is a toolkit for web developers, previously known as Zen Coding. It will greatly improve your HTML and CSS, taking snippets to a whole new level (CSS-like expressions that can be dynamically parsed and more).
Boot Metro is a flexible, simple HTML, CSS, and JS framework for web apps with a Windows 8 App Store style. It's open source and built on top of Twitter Bootstrap, and was inspired by Metro UI CSS.
Apigee is a service for developers to more easily create cutting-edge apps. Apigee handles mundane tasks like sign ups/log ins, storage, and server maintenance, alongside plenty of other features.
Rosarian is a brush-style script with thick, round shapes and variable line widths. It was designed by Laura Worthington, of Umbrella Type.
Hummingbird is reminiscent of old-fashioned penmanship, with technical sophistication. It is airy, personal, sensual, and has irregularities that make it as innately and intimately human as a writer's hand and pen.
Eaglefeather is based on an alphabet designed by Frank Lloyd Wright for the "Eaglerock" project in 1922. It's been adapted by P22 Type foundry.
Poly is a free display font with geometric sensibilities. It's great at large sizes and comes with a number of alternate characters.
Toolkit is a free display typeface with letterforms reminiscent of hand tools, including rulers, squares, wrenches, and more.
Zombie Sunrise ($10)
Zombie Sunrise is inspired by vintage horror films from the 60s. It's hand-drawn and was designed by David Alexander Slaager.
Window Dressing JNL ($25)
Window Dressing JNL is based on a picture of cast metal letters from the 1950s. It has clean, simple lines, and unusual letterforms for the B and R.
King Wood Volume ($100)
King Wood Volume is a gothic typeface with Tuscan flair, that works equally well in designs inspired by the west or the east.
Moki comes in seven different styles (Base, Cut, Dust, Lean, Mono, Soft, and Uni), perfect for display use.
RBNo2.1 is a condensed sans-serif font with a geometric appearance and technical style. It has two versions in seven weights, with matching italics.
Did we forget something you think should have been included? Let us know in the comments below!