On the ultra-cheap end I got the SYNET7LP. I paid US$99 on Ebay, and I see a seller there now has it for US$79:
http://www.ebay.com/itm/Sylvania-SYNET7 ... 336bd559c5
It has a resistive screen, which is mildly annoying but not too bad once you get used to it. I got the SYNET7LP primarily to see what the low-end experience is like, and for that it delivers in spades.
Still, not too bad for the money, and it's also a good test machine for rooting if that sort of thing is of interest (for what I paid I don't really care if I screw it up <g>).
I don't know of any capacitive-screen tablets for under $250, but if you could raise your upper range to $349 you can get what is perhaps the best tablet available in the world today: the Asus Transformer.
I love mine. A lot. Great screen, both larger and higher-res than my iPad 2, with the blazing fast Nvidia Tegra 2 processor and similar battery life to the iPad 2.
The Android Honeycomb it ships with rocks. And I mean rocks! After enjoying the flexibility of defining my work spaces with widgets, I'm convinced that iOS 6 will add widget support; it'd be silly not to.
The Transformer lists for US$399, but if you shop around it's not hard to find it for $349. A bargain, at even the full list price, IMO, since it's such a joy to use.
I initially got mine just for testing, but I fell so in love with it that just days later I went back to the store to pick up the optional keyboard dock, providing a netbook experience for the device and contains its own battery, double its battery life up to 16 hours. The keyboard is a reasonably responsive chicklet style, and with it I can write extensively and even do server admin with the device. I've since retired my netbook; now the Transformer is both my favorite tablet and my favorite netbook.