Ohne Gewähr, meine Interpretation:

Goods for sale: Sachen zu verkaufen - Z.b. this house is for sale.
Goods on sale kann 2 Bedeutungen haben:
1) Sachen werden hier verkauft (in einem bestimmten Laden)
2) Sachen im Sonderangebot: the dress was on sale - das Kleid war im Sonderangebot.

Not sure about #1.
I would translate "im Sonderangebot" with "in the sale".
IMHO "on sale" means generally "available in shops, etc."
Tomatoes are on sale everywhere.
"For sale" is more specific.
This house is for sale.

in the sale? I have never heard that used.

"on sale" to me means im Sonderangebot.

"Toilet paper is on sale this week at the supermarket." -> "Im Supermarkt gibt's Toilettenpaper zum Sonderpreis."

@ Lara Chu: Obviously there is some difference between US and BE usage.
A Brit would translate your example as meaning "Es gibt diese Woche Klopapier im Supermarkt zu kaufen". (Maybe the sort of sentence one might have heard twenty years ago in Bulgaria.)

Interesting; learn something new every day

Hm, Tomtom, ich wollte grade fragen ob Du BE native bist - ich bin seit 6 Jahren in London on habe "on the sale" auch noch nie gehört - höchstens "in the sales this week", aber selbst da wäre ich mir nicht sicher...aber ich würde da jetzt auch nicht meine Hand ins Feuer legen :-)

@ Vero:
Yes, I am a BE native speaker.
I think "in the sale" or "in the sales" is quite common. (Was your "on the sale" a typing error?).
"In the sales" would more likely refer to the big sales e.g. after Christmas when almost all shops have sales.
If I refer just to one shop, I would say "in the sale".

Tomtom, yes that was a typo, my bad! Really don't want to question your English abilities (:-)), but might this be a regionalism?
"In the sale" doesn't get many hits on google (and yes, I know it's a very questionable way of assessing the common usage of a phrase :-))

As another BE native speaker, I would use the expressions "in the sale" and "in the sales" in the same way as Tomtom. I have never considered these phrases to be regional, though you never know...

For AE #1 is right.

For sale - zu verkaufen
The house is for sale; I saw a "for sale" sign in front of the house.

On sale -
1. im Sonderangebot: I bought this shirt on sale.
2. zu verkaufen: Hula Hoops are on sale everywhere. (I think this still implies at a somewhat reduced price.)