Learn Icelandic: Ræðum uppboðið í dag! - Let's discuss the auction today!

By putting the 1st person plural ("we") form of a verb at the very beginning of a sentence, you create an exhortation—a suggestion to do something together. When you use this verb-first word order, you drop the pronoun við (we).

Could I use við skulum to make this suggestion instead?

Yes! You could say Við skulum ræða uppboðið í dag! Both mean "Let's discuss the auction today." The Ræðum... version is just a bit punchier and more direct, while using við skulum followed by the bare infinitive (ræða) is another perfectly natural way to say it.

What case is uppboðið, and why?

It is in the accusative case because it's the direct object of the verb ræða (to discuss). Uppboð (auction) is a neuter noun, and for neuter nouns, the nominative and accusative forms are identical. The -ið at the end is the attached definite article, making it "the auction".

I know dagur means "day", so why is "today" translated as í dag?

Icelandic frequently uses the preposition í followed by a time word in the accusative case to refer to current or upcoming points in time. While í dag translates literally as "in day," it is the standard fixed expression for "today." You will see this same pattern in other phrases like í kvöld (tonight) or í sumar (this summer).