you ought to try out
callwave. it works as an online internet answering machine and takes calls while your online, then downloads them and plays them for you, all without having to get offline. it's great and the download of the message doesn't take very long even on my slow (26.4kbps) connection. it does cost a few bucks a month (like $3 i think) but it's much better then missing calls or having to get offline when people might call.