You can do this in MT by changing the date on the post to something in the future; that will force the system to always display it before everything else.

GM has a nice feature that allows one to check a box and the post will remain at the top of the page even after other entires are added. This can be really handy when making annoucements and the like. A checkbox to do that would be a nice addition.

Cordially,
Dodd

Oh, and here is another (better) way to do it, originally posted by shmuel.