Is "classic dot battle dot net" down? Are there any well-organized alternate sources that list all the item info and cube recipes?

I literally just came here to write the same thing, yes website seems to be down atm. Strange times

I hope they fix it soon - I have a ton of junk to sort out and need to know item min/max stats on what to keep/toss.

Is that Arreat Summit?

yea

Without that website it'll be impossible to play D. I hope JSP clones it.

not needed, plenty of websites with identical or better information around
if you are looking for item stats:
https://diablo.fandom.com/wiki/Diablo_Wiki
if you are looking for game mechanics:
https://www.theamazonbasin.com/wiki/index.php/Diablo_II
D2L attack speeds:
https://d2.lc/IAS/
D2R attack speeds:
https://warren1001.github.io/IAS_Calculator/

Affixes
https://planetdiablo.eu/diablo2/itemdb/affix_index.php?lang=en&version=lod&patch=111

https://d2grail.com/items

Lacking cube recipes but no ads is nice

Not quite as concise as the original but they help a lot. Thanks.