Correct usage

There's not much context to go on, but I'd say it depends on what you want to say.
1. You could have multiple presentations on a single scholarship - scholarship presentations
2. a single presentation on multiple scholarships - scholarships presentation.

Again, without much else that's about the best I can come up with. Anyone else?

I think you mean you are giving out scholarships at a formal ceremony, right?

In which case "scholarship presentations" sound better if you are taliking about the act of handing them outor presenting them to individuals. If you are talking about the ceremony itself then it would be singular "scholarship presentation" (unless of course your talking about multiple ceremonies.

In general when nouns are used as ajectives, they take the singular form:
Hamburger shop, not hamburgers shop

But there are always exceptions. Can you give us the context?