Choose between video download or receiving a DVD. Some courses offer a lower price for audio-only, and most come with a guidebook. You can often pick up audiobook versions of The Great Courses at audible.com at a considerable discount, minus the course guidebook.

Categories are split into science, history, fine arts, economics, literature, philosophy, religion, mathematics, high school, better living and professional, with 25 to 200 courses in each.

Most courses are free and let you learn at your own pace, giving a rough indication of how long it will take, as well as a difficulty level. These free courses also offer a paid, verified version, which includes graded assessments and a certificate from the university.

Other courses are paid-only and include assignments, regular group discussions, instructor feedback and live video chats. Similar to a real university course, they follow a stricter schedule.

There are also professional resources from companies such as PWC, Goldman Sachs, Intel, and IBM.

Partners include the University of NSW (UNSW), University of Sydney, Macquarie University and University of Melbourne, as well as overseas institutions such as Yale, Princeton and University of London – 145 in total.

Courses come in themed sets called specialisations with coursework including hands-on projects and real instructors, culminating in a certificate of completion. Some specialised courses take a few dozen hours while others can take months of 10 hours or more per week.

Courses range from the broad – such as marketing basics – to the more specific, like how to conduct business-to-business marketing on social media platform LinkedIn.

There are thousands of short courses and over a hundred categories, often around five hours in length (but this can vary), with video tutorials, transcripts and exercise files you can download.

Topic categories include web development, design, business, IT and software, personal development, marketing, music, and photography.

Courses can include over 40 hours of video, dozens of articles, and downloadable resources, as well as a certificate of completion. However, not all their courses are so generous – some have just one written article, few downloadable resources and less video content.

Other topics include editing and writing for film, singing, design and architecture, tennis, comedy, business skills, fashion design, performing arts and even space exploration by ex-international space station commander, Chris Hadfield.

Each personality has created their own course of video lessons, usually between 20 or 30 videos apiece. Upload your own video using what you've learned and you may even get personal feedback from the teacher.

Courses can be taken and paid for individually, or you can pay $280 for an all-access annual pass.

Courses are created by community contributors who work together to build a polished product with in-depth exercises ranging from basic to advanced. Language lessons incorporate reading, writing, listening and speaking exercises – utilising voice-recognition software.

If you find something tricky, there are user-generated comments for each section that can help.

Duolingo is free on PC web browsers or available as an app on iPhone or Android. The apps come with ads, but you can pay a subscription ($14.49 for one month, $65.99 for six months, and $109.99 for 12 months) to geo ad-free and also gain offline access to lessons. The web browser version has no ads.

The focus on conversational language can help if you're brushing up for an overseas trip.

There are also specific segments on pronunciation, or the more unique or quirky elements of each language's grammar (from an English-speaker's perspective).

Individual sessions start at about $49 per lesson for beginners, up to $83 for advanced. Children aged 3–12 pay just $35.

There are also group lessons at all difficulty levels, which go for 60 minutes for $25 per student.

Learn over live video chat with professional instructors (webcam required), but this is a global service, so some time zone finagling may be required.

Choose a tune and play along on your instrument (you can even upload your own songs). The app listens to you play and gives feedback on accuracy and timing, along with historical statistics on your progress.

There are also expert-designed courses that let you choose between learning different styles, such as rhythm or lead guitar. The difficulty level extends from complete beginner to professional.

The free version limits lessons to 10 minutes per session. The premium subscription allows unlimited play time with access to guided lessons

Class categories include 3D printing, CNC (computer numerical control), electronics, workshop, sewing, craft, food and design. There's also a kids' section to entertain younger members, and some classes are free.

And there are lots of do-it-yourself projects, such as how to make your own adjustable-height table using a car jack, building a basic toy robot, binding your own book, or making an acoustic guitar from scratch.

There are also some general knowledge resources, such as how to identify old glassware when antique shopping, cleaning tips, and advice for different painting styles.

Instructions are often not as detailed as they are on Instructables, nor do they have as many visual aids. They are free, however, and it's easy to browse specific categories in search of a project that catches your eye.