The two Auron mentioned are good, other possibilities include:
1) Ground, Fire, Grass
Maybe a tad too similar the classic starter types, but works fine match-up wise.
2) Ground, Electric, Water
Only problem here is that Ground is immune to Electric.
3) Rock, Bug, Grass
Grass doesn't resist Rock, otherwise works perfectly.
4) Ground, Steel, Ice
Somehow this one actually works (who ever knew Ice was weak to Steel?), lesser used types too so that's nice.
5) Psychic, Poison, Bug
I like this one a lot, because it's completely different from the usual starters. Also, I'd love to use a bug-type starter.
6) Fire, Rock, Steel
This one would also be cool.