Hardware is dirt cheap on eBay. I learned a lot when studying for the ccna, but I learned the most from buying gear off of eBay and playing with it.
My favorite project was the PSTN simulator I built using a Cisco 2821. I still remember my biggest issue when setting it up- I used Audacity to cut out 15 second segments of different songs to use for various types of calls (local, long distance, 900, 800, international, 411, 911, etc). When a number was dialed it would play back the corresponding song so I knew I had all the call routing done properly. When I first set it up it didn't work. When I ran debugging, I was getting an error message about some issue with the channels. So naturally I think it's a problem with the VWIC configuration. I spent literally hours pulling my hair out trying to find the problem. And you know what it ended up being? The audio files were in stereo and the Cisco 2821 could only do mono. Fuck me, I was so mad, but it's kinda funny looking back on it. I learned a lot that day.