An extra module seems excessive, but you might look into the jskit embeds. They might be more to your liking.

Or for that matter, just add [[module Comments]] to the link submissions page and let them submit links as post comments.

It requires users to log in and create a new page which is not the "simply paste and hit enter". Users would also have to give the new page a name. No one would like to have to wonder how to name a page with only one URL in it.

Maybe there should be a module for submission of URLs?

Add rss="links" to the ListPages module, and it will provide an RSS feed. Alter the "limit" to suit the needs of the page.

I was thinking to embed a meebo widget (pros: I can review links and filter spam, etc; cons - the link doesn't instantly appear on the page).

I prefer, though, the user to be happy to see his or her submission instantly on the page. (If not on the page, at least on some "links pending for inclusion" section but I want the users to know that what they've sent has reached the destination.) For filtering spam I'd like to have an RSS notification on any new submission so that I can delete inappropriate links if necessary. But how could that be made without great complications?

The PetitionAdmin module seems interesting for the purpose as well as the [[include]] command (e.g. "[[include include:embed]]" in http://community.wikidot.com/embed).

What would you advise me? Btw if you think [[include]] is best, please add instructions how exactly to make it work, I have no idea how exactly it works.