Now, this isn't the cheapest tablet I've purchased, but it is the one with the lowest retail. This tablet from Hong Kong based ESER is based around a 7" (800x480) resistive touchscreen, and it has 4GB Flash storage, a microSD card slot, Wifi, HDMI out, USB Host, and a front-facing webcam.
It's running Android 2.3 Gingerbread. It also has a speaker and mike, and according to ShanzhaiBen you can use ot for video chat. The USB Host also supports 3G dongles, but as you can see from the next photo you'll also need to use a converter.
The specs aren't much, but so far they've been comparable to most of the decent $100 tablets. But what makes it really cheap (besides the fact it's in China, the world's most competitive tablet market) is the CPU. This tablet is using the new BoxChip CPU, the one with 1.2GHz CPU and a 400MHz PU built into the one chip. That is an exceptionally popular CPU at the moment because (according to the manufacturers I've talked to) it offers excellent performance for the price.
It's so good that this tablet reportedly can decode a 2160P video. I'm not sure anyone is making a video with that resolution (the current standard for HD is 1080p), but if they did this tablet could play it.
Pretty cool, huh?