Thanks for your reply!
I unchecked “Attempt to notify any Weblogs linked to from the article (slows down posting.)” – but no change. I try to post a link to amazon and it takes as long as before.
And another thing: this section in the Options > Discussion settings tells me “These settings may be overridden for individual articles”, but I cannot find any checkbox or button in the article form. (I did not change any pages in the wp-admin directory, just my theme)
Can you tell me what WP is doing exactly? Amazon pages are usually big and contain lots of links, is it that? Could it be a problem with my web hoster? (But I used Serendipity for testing on the same server and posting wasn’t that slow.)