Debian + Ubuntu packages are in place. You can ping me about them. (I hope I can get 1.5 into Ubuntu 9.10 but there's some delays so I'm not sure).
For the other distros, you'll just need to convince someone to do the work
The easiest way is providing a really nice fee game the distros want to ship as library packaging in general is rather demanding and more ikely to be done if there are other packages depending on them.
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and as laurent said, this is in nearly all cases not the task for the upstream project. SFML is (I guess) a quite demanding thing for a single developer even without having to care for X distributions