Typically, you export .flv out of Premiere, and then bring that into Flash for .swf authoring.
This is simiar to the DVD workflow where you export out .m2v files from Premiere and bring them into Encore for DVD authoring.
But for quick and easy web video, I use a program called V2F. Can't recommend it highly enough.
As Jim said, using Adobe Flash to import the .flv and create a .swf file is the typical workflow for that process, but if you just want to convert .flv files that you've exported from Premiere into .swf files, I suggest Super Converter by eRightSoft. It is a free download, and is one of the best all around converters that I have worked with.
I checked out both apps and, even though V2F is not very expensive, you can't beat free :-P. Now I wanna know what is a good bitrate for flash videos that would give me a balance between best quality and good streaming size. The videos I wanna make aren't long, maybe 30 secs long, so I might be able to get away with a bigger size to maintain quality, right?