Sorry for the late reply, as I was busy working... on my mountain biking skills yesterday.
Alright, the secret is there is NO SECRETan easier way that leads down to the bonfire in the swamp and you only have to fight 3-4 enemies (not including mosquitos) to get down to it. I wasn't going to tell you this before quelaag though, that's no fun.
You need the master key starting gift (or buy from a future npc down the road), and the shortcut is in a tower in new londo ruins (right below the firelink shrine). I'm telling you this now because it will make future trips down there (and on new characters) about 15x less stressful.
Basically, the path will look like this
1) Firelink shrine
2) New londo
3) Valley of the drakes (where you can nab a pretty good dragoncrest shield and a decent astoras straightsword which if I remember correctly has decent scaling with faith
4) Blighttown, go down.