Very open ended question... You don't indicate your interests so it's hard to give specific responses.
That having been said:
1) Tripods are permitted in the temples
2) get a guide to take you through angkor wat - you will get a lot more from the experience
3) take in an apsara dance in town - there's a hotel that has a smorgasbord dinner + dance show from 7pm for about $15 it's almost opposite the Lucky Mall complex
4) after a long walk through the temple complexes, go to one of the massage centres. They are NOT all knock shops, there are many genuine places that can revitalise feet (I love "master feet" in street 2 opposite blue pumpkin)
5) forget the balloon ride, it's not worth the money.
6) if you find that 6 days is a bit too much here, you could take a flight to PP and visit the genocide museum / killing fields. There's an airline (Bassaka (sp)), who have rock bottom prices and it's a quick 45 minute flight from one city to the next.
7)the Artisans d' Angkor is worth a look in - no pressure to buy and, some lovely work created by people.
8) the crocodile farm is a bit miserable, but if you've never seen crocs up close, it may be of interest.
9) for markets, there's Psa Leu and Psa Cheu that offer bargains - clothing, DVD's and more
10) for gastronomic indulgences, try some of the hundreds of restaurants in pub street and surrounds. One of the best I've found at this time is th Khmer Kitchen - slightly higher prices than some others but the portions sizes are good and, all meals come with unlimited free rice.
That should give you a reasonable starting point for your journey here.