They sell umbrella style swifts at Knitpicks for $65 US but I just couldn't bear to spend that much when I could wind skeins of yarn by hand. That was how I used to wind skeins before - I would spread the skein over my knees and make a ball by hand. It took me 20 minutes per skein and I hated it.
I did invest in a Knitpicks Ball Winder, which was about $20 US. I think it is totally worth it to buy a ball winder to go with a swift. It makes the whole process so fast and almost effortless.
Back to the swift though. My husband spent about 2 evenings working on it. He bought all the supplies for about $20. That included a lazy susan type plate which allows the swift to rotate easily. I think you can do it without the lazy susan by using other hardware too. He used basic tools - a drill, a saw and purchased the wood and dowel in the widths he needed.
I think he really enjoyed making it and he loves seeing me use it. He does worry that it goes too fast, but once you get into the rhythm of it, speed doesn't matter too much. Now it takes me about 4 minutes to wind a ball of yarn. I can access both ends for knitting with two strands too (yarn shown is Berroco Jasper).
I have my ball winder set up on a lap board. I like this method a lot and it means I don't always have to take it on and off the table.
I tried to take photos of the swift in action, but it was too hard for me to do on my own. It's hard to take photos of the swift in general, since it is quite large, but I think these will at least give you an idea.
I highly recommend having both a swift and a ball winder to deal with skeins, but, now you have an inexpensive option for getting a swift!
For Ravelry Members, you could also check out the DIY Tool Forum. People are making swifts (and other tools) out of lots of neat things (lego!).