Are there any good SaaS apps for inventory/stock management?

I don't need anything fancy, like barcode readers or anything like that just yet. All I want to be able to do is keep track of the stock I get from my vendors and the necessary info - quantity, price, etc. The same for sales, I want to see what each customer orders, and be able to generate a nice invoice. I should also be able to plot these things over time...to see how my prices fluctuate along with my costs. I would also like to be able to see my margins on cost of goods, etc. - and be able to change them easily. Anybody know of something like this?