"The Street" was written in late 1919, and first published in the December 1920 issue of Wolverine. (No relation.) Supposedly inspired by the Boston police strike, it tells the history of a street, which starts out well, but is eventually brought to ruin by Lovecraft's greatest horror - swarthy non-Anglo-Saxons!
"The Doom That Came to Sarnath" was written December 3, 1919, and first published in the June 1920 issue of the Scot. It tells the story of an ancient city that suffers the vengenace of an even older race of inhuman beings. It's a wonder these elder races got wiped out, there were so many of them.
"The Statement of Randolph Carter" - written in December 1919, it was first published in the Vagrant of May 1920. Two men investigate a hidden stairway in a lost cemetery and discover that it was a bad idea. We'll see Carter again, I believe. This is the first story to mention a "forbidden book", although it remains unnamed.
"The Terrible Old Man" was wirtten on January 28, 1920, and first published in the July 192 issue of Tryout. Three "ethnic" burglars ( a Pole, an Italian and a Portuguese) decide to rob a weird old guy who is known to keep alot of money around the house, and maybe it doesn't work out so well for them. This story has the first mention of the fictitious town of "Kingsport". The beginnings of another Lovecraft trope - old sea captains have invariably been to strange and terrible places and learned strange and terrible practices and brought them back to New England. As if we didn't have enough strange and terrible practices of our own!
"The Temple" was written in the latter half of 1920, and first published in the September 1925 Weird Tales. In it, a U-Boat captain, the last survivor of his sunken vessel, discovrs a mysterious underwater structure. The protagonist is very much a stereotypical "haughty Prussian officer" type.
"Facts Concerning the Later Arthur Jermyn and His Family" was written in the latter half of 1920, and first published in the March and June 1921 issues of Wolverine. It was later anthologized as "The White Ape". The descendant of an English explorer that went to Africa discovers facts about his ancestry. Essentially, a parable about the dangers of race-mixing.
"Celephaïs" was written in November 1920 and first published in the May 1922 Rainbow. In it, a lonely man dreams of life ina fabulous city. Notable for the first mentions of the "plateau of Leng" and the fictional town of "Innsmouth".
"From Beyond" was written on November 16, 1920, and first published in the June 1934 issue of Fantasy Fan. It's the story of a scientist who devises a way to see the way the world around us really is, and sees more than he bargained for.
"Nyarlathotep" was written in December 1920, but first published in the November 1920 United Amateur - this apparent contradication is explained by the fact that the UA tended to come out long after its cover date, for some reason. It's a "prose-poem" about the arrival of a dark prohpet. Quite eerie in its way.