You just missed a few good deals this past week, Dell had an Inspiron 11z i3 330UM for $300 and Staples had an Aspire AO722 C-60 for $250.
I bought a used AO722 on Ebay for $205. I picked it up for basic browsing and web development and I'm happy with it. If you plan on doing any compiling on the laptop itself you might want something with a little more power.
11.6" 1366x768 is the perfect form factor for me, but I also do a lot of browsing on a 480x320 Palm Pre so I'm not very demanding. I undervolted the C-60 and downclocked it a bit to 1ghz (stock is 1.33ghz Turbo) and I get 6 hours of battery life with Wi-Fi on, not sure how much the previous owner had taxed the battery either.
From what I've read the Inspiron 11z has a battery life of about 4 hours. The C-60 is roughly on par with Atom, a tiny bit faster in some cases. I watch 720p videos on Youtube pretty often so I went with an AMD Fusion netbook. If you're ok with 480p streaming video and plan on doing all your compiling on a desktop you might even be fine with an Atom based netbook, some of which can get 9+ hours on a single charge.
Other options are E-350 netbooks (slightly faster than a C-60) like the Lenovo x120e and HP DM1. Personally, I would never spend more than $350 on a laptop, I don't understand why some people are willing to drop a grand or more on something that ages so quickly, but different strokes I guess.
A few things I don't like about my AO722 are god awful viewing angles and not the best keyboard layout. Home and End are Fn keys, for coding that's a bit of an annoyance. I'm not sure why so many tablets come with IPS screens, some in the $200 range, but only a few high end laptops have them. I'd be willing to pay a little more for a netbook with an IPS screen.