In any economic downturn, it’s a good idea to assess your professional development. It’s an especially good idea if you find yourself “between engagements.” But tough financial times often rule out full-time school or even night school, especially if you’re seeking specific skills to enhance or maintain your employability. You need a training regimen that fits your schedule and won’t break the bank, and that’s what this roundup of budget-conscious self-training tools gives you.

The offerings gathered here represent some of the highest quality and least expensive self-training options out there. You’ll find them a quick start to your ongoing professional development regimen. In one sense, the Internet itself is a single giant self-training tool, and whether or not you dig into any of the resources listed in this roundup, it’s always a good idea to scan the web for useful tools. New opportunities pop up continuously.

Low cost tools come in two flavors: cheap and free. Good quality free training is hard to find, but, thankfully, half of the listings here fall into that category. Even the fee-based offerings are inexpensive, and will probably cost you less than your Starbucks habit. The average cost for the paid training systems is about $25/month, and you can lower that cost by paying for a year in advance.

I’ve only listed training that you can take online, but that doesn’t mean the courses are limited to online access. Some let you download materials as PDFs, DVDs, or video files for offline perusal, and some let you print paper copies for truly unplugged study.

Figure 1 summarizes the features of each offering. For most courses, you only need a standard web browser, and the table indicates the few vendors that require a specific viewer. The list is short enough that you should take time visiting each vendor’s site to get a deeper feel for the available content. You’ll likely find something worthwhile at each.

Here are some notes for each of the training products:

Apple’s iTunes University. This is truly a perpetual student’s dream: actual University-grade courses, presented as video and audio lectures with collateral material such as syllabi and exercises. Tuition: zero. Does zero work for you? (No college credit is granted for iTunes U courses). An advantage over actually attending class is that you can rewind and fast-forward the talking head to match your learning pace. You may need to purchase the associated textbook, but that can be done online at Amazon and other web bookstores.

Association for Computing Machinery. The most expensive up-front self-training package of those listed is also the best overall value. For $198/year you get access to thousands of top-notch training videos, plus virtual labs that let you run computing and networking exercises on actual hardware, such as Windows servers and Cisco routers. You also get access to the ACM’s Digital Library, a mountain of technical journals, magazines, and other publications. As a member, you receive a tony acm.org email address as well

Google Tech Talks. For a company that didn’t exist twelve years ago, Google sure has made an impression on modern society. One of those impressions is the vast collection of lectern lectures given by visiting experts on the Google campus (called the Googleplex, naturally). You’ll hear from Google employees—in-the-trenches programmers and engineers—as well as Google executives, such as founders Eric Schmidt and Sergey Brin and Internet innovator Vint Cerf. My favorite talk is one by Radia Perlman, inventor of the Spanning Tree protocol, titled Routing Without Tears, Bridging Without Danger.

IBM Redbooks and Redpapers; free IBM courses. Anyone who's worked with IBM i technology for very long knows about IBM Redbooks and Redpapers. These printed tutorials, usually created by small, focused workshops of IBM technologists from around the globe, are the “missing manuals” to IBM systems and software. They often unlock secrets and shortcuts that make the difference between going home when it’s light and when it's dark outside. And although IBM is famous for expensive professional training courses, the IBM web site hides more than 1,000 totally free self-study aids that are worth many times what you pay for them. Or something.

Lynda.com. A key to fast learning is consistency in the quality and depth of training materials. Lynda.com has both high quality and excellent consistency for a very low price: $25/month buys you every course in their large library. Because Lynda.com creates all its own courses (overseen by Lynda herself—she’s a real person), the syllabi fit together well, letting you assemble a curriculum tailored to a specific career goal. Lynda.com subjects tend toward Mac rather than Windows applications, although Windows is covered in many of the dual-platform courses, such as Web design and digital imaging.

O’Reilly Safari Books Online. Have you ever needed a technical book like, right now? And run around town trying to find it in a local bookstore? With O’Reily’s Safari, you can eliminate that danger for as little as $23/month, which lets you read online (and print, in many cases) any book from a huge library spanning tens of thousands of volumes and dozens of information technology subjects. Safari also has video courses, pre-release manuscripts you can “beta test,” and a slew of tiny books called “shorts.” The low-end subscription lets you check out ten books per month. For twice the price, you get all-you-can-eat access. Which is what I have, neener neener.