To repeat the above, T-Racks 24 is great for a dose of analogue punch and I've also used the O-Zone plugin but I reccomened T-Racks for anyone new to mastering as it is more "hands on" and intuitive...

problem I have with these progs (pureley my own fault) is its far too easy to go overboard on the mastering front so you are almost using it as an effect on its own, as opposed to finalising a mix (if you follow me..)...so my top tip for all mastering is to:

* Adjust all paramters till your track sounds schweet..
* Pull everything down slightly
* Pull them down some more....

Also I reckon its good to have some mates come over and have alisten so you have 3 or 4 different masters err, mastered then wait till the next day to decided on which one you prefer....

Ramble over...