It was advertised in Holy Temple of Mass Consumption issue #20, as found on a Usenet archive: REINCONATION 3. Radisson South, Bloomington MN; rms $63. GoH: Debbie Notkin; guests: TBA. Memb: $18 until 7/20/93, $25 after (children $7 until 7/20/93, $10 after). Info: Reinconation 3, P.O. Box 8297, Lake Street Station, Minneapolis, MN 55408. Guests of honor were Joan Vinge and Debbie Notkin (as also stated above). Geri Sullivan was publications head. Here's a short con report.
Eventually, we should have scans of at least the second progress report, program book and pocket program here.
There were 119 pre-registered members, counting the two GoH, and 88 at-the-door, for a total of 207 members, of which 194 showed up as warm bodies. This comes from counting the names on the sign-in sheets, plus the count of at-the-door sign-ins, except that there are only 83 names there, but a tally apparently done on the spot uses 88 for the sum. It seems likely that 88 is correct and the last 5 just didn't get written down in the same place (maybe they registered on Sunday). This tally sheet gives 217 as the total, but it looks like this is an arithmetic error.
An ad for ReinCONation 3 appeared in the Minicon 28 program book, page 5.
You might also be interested in the ReinCONation index page, used for ReinCONation 5, 6, and Not-A-ReinCONation.