Intel Chipsets

Well, it depends on what you want to do. The Differences between the north and south bridge are:
North bridge generally controls/manages things like the cpu,memory,vga card. Things that need to go fast basically. The south bridge controlls things like sound cards, I/O cards, and harddrives. Those are the main differances.

As for wich combo is best, it really depends what you want your machine to do . I dont know much about the southbridge choices today, but for the northbridge a p35 is a nice solid chip. It overclockes very well also. But say you want to build a hometheater pc. The a g35 would be better. It all depends. What will you use your computer for?
Also keep in mind, Nvidea makes northbriges also, which are needed for sli.

If you're on a bit of a budget P35 northbridge, if u'r not on a budget then X38's are great, if you have cash to burn for no good reason then an X48 northbridge, but really that's only if you would rather donate money to intel instead of literaly setting it on fire.

For south bridge, ICH9 and if you want to set up raid ICH9R.

The DS3L won't do RAID, but the slightly more expensive and otherwise identical DS3R will.