I've had good luck using a last gen 12" pb for a netbook. With the ram maxed out (and a hd upgrade), it's a pretty capable machine for browsing, emailing, word processing and the like.
You may be able to coax a little more life out of the battery by wrapping it in a paper towel, sticking it in a sealable baggie and putting it the freezer for a day or two. Another option is ebay, craigslist or 3rd party repair shops for a spare battery. I goosed a little more life out of my existing battery after one or two stays in the freezer, and got a spare battery a 3rd party shop used to use for repair purposes and didn't need anymore-it had 98% original capacity!
And, there's a couple of sites online about maximizing an older mac's performance using tiger or leopard by disabling unnecessary processes and unneeded eye candy.
I'm not sure if your ibook's gpu can handle online video on the likes of youtube. My pb had a slightly better processor with twice the video ram, and it can barely handle sd video-HD is out of the question.
My dad recently bought a 1.07 ghz 12" g4 ibook, and it allows him to browse and pursue the mobile iLife fairly well with 768 mb of ram.