I found a good link about this topic a while ago, it's a bit outdated, but I'm sure it mostly holds true:
http://www.thewarp.net/war/tigersofveda/1000polsm.htmlPersonally, I do wierd armies, so this is probably not the "best" of ideas proposed below, but I'll dish it out anyway:
HQ:
Reclusiarch, with termie honnors
command squad: 4x marines w/ BP & CCW
Vet Sargent with BP & PF
Squad with Infultrate Skill and fragnades
Troops:
Scout sniper squad, 4x rifles, 1x sargent
Tactical squad one: 6x marines, 2 w/ plasma guns
Tactical Squad two: 6x marines, 2 w/ meltaguns
Tactical Squad three: 7x marines, 2 w/ flamers
Vet Sargent w/ BP & PF
Fast Attack:
Assault Marines 5x marines, 2/ Plasma Pistols
Sarge w/ BP & PF
Heavy Support:
Whirlwind.
You'll need to buy.. what, a small command squad (4 marines + sargent) the tactical squads (19 marines n' a sargent) a single assault marine, and a whirlie.
Lets see... 3x SM boxes (105$) a assault marine (10$) and a PF sargent (10$) and of corse the whirlwind (40$) that should run around 165$ unless my math is horribly off, and will give you a few spare marines for when you start expanding the army beyond the 1000 pt mark, heck, it gives you most of a missle-launcher equiped devistator squad... although, you really probably shouldn't use missile launchers in a dev squad, but that's a different topic entirly.
now, this might not be a very effective list, what can I say, I've spent the whole day alternitavly sleeping and throwing up into a bucket, so it seems good at the moment.
Edit: Checked and corrected my prices. Also realized that the tactical squad box comes with flamers, heh...
Another edit: erm, just realize that the tactical squad box also comes with plasma guns and flamers... what can I say, I'm just not on top of things these days.