Usually if you do the battery calibration procedure recommended by Apple you can at least get it to tell you accurately how much time you've got left, so you don't get "sudden" sleeps. Sometimes this can even recover some of the "lost" battery capacity, although I wouldn't get my hopes up.
For an older laptop an hour really isn't that bad (heck, I borrowed an older Dell laptop from somebody that literally wouldn't last 5 minutes on its battery), but if it's not long enough for you FastMac is one option (their 12" iBook battery is 4400 mah), or you can try the nuPower batteries that OWC (macsales.com) sells--they have a 4100mah one for $100, or a 5000mah one for $130 if you really want to max out the runtime.