If you're using Apple's Mail.app (and chances are, you do, if I look at my referer logs here ;-) you either a) definitely need to know about or b) already heard of the two following neat plugins: GPGMail and Mail Act-On.

And if c) you're already using one or both of these you still might get something out of this entry: both bundles have been updated just recently for (among other things) improved Tiger compatability.

So there you go, I thought I'd let you know ;-)