I have no idea why I have that for the B. I think because I used a colon!!

I stayed at Hotel Helmet in Warsaw. It's a business type hotel across the river from the Old Town. There are few hotels in Old Town - I only know about the Castle Inn but I think that's more than $100/night.

You can take the bus from the hotel to old town square although we took taxis. Taxi rates double after 9:00PM so while the day rates were reasonable the night rates were not.

There are quite a few Krakow hotels recommended here recently. The hotel I stayed at (Trecius) is closed for renovation until the fall (can't remember when you are going). Stay as close to the main square as you can.

We stayed at Hotel Saski in Krakow in 2003 & were very happy there. It's in an excellent location, about 1/2 block from the main square. At the time, the price included a very hearty & delicious breakfast, which consisted of a buffet & eggs cooked to order.

In Prague, twice we stayed at the Pension Dietzenhofer in Mala Strana, which is the same side of the bridge as the castle. It's quieter than Old Town Square & Wenceslas Square. price also includes breakfast.

In that price 100$/night you can find many nice hotels in Warsaw. Of course if don't plan to stay in Warsaw during Euro2012
If you want to stay in city centre check:
- Mamaison Residence Diana Warsaw (Chmielna street, 10 minutes to Old Town by walk)
- Novotel Warszawa Centrum
- Warsaw Marriott Hotel
- ibis Warszawa Centrum

More about hotels: www.findwarsaw.com/accommodation/hotels-in-warsaw

Krakow and Budapest are the cheapest cities from this list. You can find an interesting place to stay there even for less than 100$ per day.

Just scored 2 rooms at the Prague Hilton in Old Town in Prague for 5 nights @ $75/per room/per night. We are going in July and wanted to ensure air conditioning and elevator. We feel pretty good about the locations, hotel got good reviews on Trip Advisor and is on top of metro station. Not really sure the location technically qualifies as Old Town, looks more like Wenceslas Square, but it will do.

Vienna tends to be an expensive city.

This place was recommended to me by a friend in Austria and I've rented from them on several occasions over the years. Super clean and some units come with its own small bathroom.

I tend to rent for at least a week at a time, but you can email them and ask if they will take shorter period stays, since I've noticed that there are people who come in for less than a week. (There are also others who stay for months!)

I know they have a website, but I can't seem to find it, so here's the Tripadvisor web entry:

http://www.tripadvisor.com/VacationRentalReview-g190454-d1577812-or6-Center_apartments_and_rooms_with_use_of_kitchen-Vienna.html#REVIEWS

We stayed here in Budapest in 2010 and would highly recommend it!

http://www.bellevuebudapest.com/index.php?lang=en&faz=1&aaz=0&kt=BellevueBudapest

LBloom, that is a great hotel, great location and great price. Did you use Priceline?