Being under 300 dollars is going to be a trick.
If your looking for a simple point and shoot there is soo many it is impossible to list them all.
Fuji fine pix, Nikons, Canons, Sonys, et al... There is really a huge list.
The one thing to consider is the lens system you want to use. If you deside on a DSLR (as mentioned above) and if your fine w/ a system like an aps sized sensor on a Canon Rebel or Nikon, then a used body from
KEH is in order. (
keh.com).
If you eventually want to up grade to a full frame sensor, then you will want to stick to that to begin with, but the cost is going to be higher. Minolta 5D or 7D you might find for under that.
Otherwise, your best bet is to start off easy with something like a Rebel with a kit lens. Again.. Look at
keh.com I would definatly stay away from systems with serious limitations. This would include Wal Mart specials.. (not so much slamming Wal mart per se...) but the reality is that they are seriously low level consumer cameras and definatly NOT designed for serious shooting.
If your sticking to the point and shoot, then I would say look at the various Nikon systems. They are good, relitivly cheap and have a solid reputation.