Hey, Michigan State fan here. Here are my views on the Big Ten fan bases, starting with my own.
Michigan State- As one of our other fans have stated, while many people think of MSU as a basketball school, we are really split 50/50. Much of our fanbase views the team as almost a sleeping giant in the Big Ten, and recently we have been "waking up". Due to this, even though we have had many miserable years, our fanbase continues to stay loyal and fill the stadium, along with traveling well. Overall I'd say while we have some downsides, we tend to be a pretty good fanbase, and I have yet to see any major disrespect toward any visiting schools that aren't named Michigan.
Penn State- Penn State fans are known for their partying, but they are also very loyal. A lot of their fans tend to look down on the Big Ten as many still remember when they were independent. Apart from that, I haven't had to many problems with them.
Wisconsin- Fun fanbase (though their basketball fans can be unbearable) and always make their gameday experience exciting. Their tradition of jumping to the song "Jump Around" during the 3rd quarter intermission always leaves the stadium shaking. There is a reason why it is so hard to win there.
Iowa- Michigan State and Iowa have been banging heads for the last couple years after Iowa fans insisted that they should jump Northwestern and Michigan State during the bowl bids simply because they "travel well", ignoring the fact that both teams had a better record and beat them head to head. They managed to jump Northwestern. Their major downside is insisting that they deserve more than they get. Apart from that, their fans are very loyal and make it very difficult to win at Kinnick Stadium. While it can be easy to get into feuds with them, nothing is ever severe enough to completely hate them. Playing their team is always entertaining though, as it always results in a physical game.
Northwestern- I haven't met anyone in their fanbase, but they have never done anything for me to disrespect them. Easily my second favorite team in the conference, and they will beat you if you don't take them seriously.
Minnesota- Being so far away, I really haven't met any Minnesota fans either. Minnesota tends to be anywhere from mediocre to bad in almost any given sport.
Purdue- They usually have a decent showing in football and basketball, but it seems to depend on how well they are doing in each sport. I never hear to much out of them, but the few that I knew were very loyal.
Illinois- All of the fans that I have met where very nice when I traveled to Champaign. They were having a losing season though, so I don't know how much that factored into it. From what I have seen, they have trouble filling their stadium, which is not very large.
Indiana- I wasn't to impressed with Indiana fans when I went down there. They were very obnoxious, especially considering how poor of a showing they were making on the field and filling in the stadium. I would be surprised if Indiana football ever made it into the top half of the conference for more than one or two years straight. Don't expect much out of them.
Ohio State- They tend to be very drunk and obnoxious, but they do travel VERY well, probably the best in the whole conference. Plan on them taking over any given stadium, though it won't be nearly as noticeable for you guys as you wear red too. If you want an idea of how bad it can get, google search images from the 2009 Michigan vs Ohio State game.
Michigan- Unbearable fanbase. Living in the same town as them makes it that much worse. They do believe that they know everything about everything, and they won't waste a second to praise the incredible education at their school...even though most of them do not and never have attended it. They truly believe they are god's gift to college football, and if they lose, it was because the refs, the time of day, the layout of the field, or the game clock screwed them over. Be prepared to hear "You would have lost to Appalachian State too...they won the Division 1-AA championship the year before."