A tiny Python script to convert a plaintext file into a MediaWiki wiki page (as wikitext), avoiding the issue that subsequent lines blend into one because MediaWiki treats newlines differently.
Basically, it adds "<br />" tags to the end of every line of the input file, except those where MediaWiki will keep the line break anyway when parsing it as wikitext (e.g. after a line that starts with "*").
I use it to publish notes taken on an Etherpad (exported from Etherpad as plaintext file) on Meta-wiki.
Usage: wikibrs.py inputfile.txt outputfile.txt
To avoid getting yourself into trouble when using this for Wikipedia articles, consider looking at the essay "Don't use line breaks" first ;)