Kalvin House Hotel

This city break to Budapest coincided with some of nicest weather in Budapest in October in some time so we managed to see a fair bit.
We stayed at the Kalvin House hotel, which was the ideal base for exploring the city, a short stroll from the Kalvin ter Metro station and about 2 mins from a number of stylish bars and decent restaurants. In addition, it's also ideally placed for the tube/bus combination that takes you to Ferihegy airport (and costs far less than taking a taxi).
Although the rooms are basic (no kettle for tea/coffee!) they are ideal if you are just using it as a base to explore as the cost (£45 per night) bought a clean, well decorated room with a plentiful Continental breakfast.
Budapest is a lovely city, and I'd recommend starting off by taking the 300-ish steps to the top of St. Stephen's Basilica for a fantastic view around the area which will help you get your bearings.
If you're looking to be well fed at a decent price, try the Trofea Grill on Victor Hugo Street - it's about £12 for an all you can eat 3 course buffet, including all drinks (you have to pay extra for spirits).
I also took the short HEV (municipal train) trip to Szentendre, which is a really beautiful little town, loads of coffee shops, gorgeous cakes & plenty of little craft shops - it's also not too commercial but has plenty to do for a day out, with a lot of museums and little nooks & crannies to explore. Bear in mind that if you go there after September, you cannot take a boat, which spoilt our return trip plans!
Most of the guide books will tell you all you need to know about Budapest, but I'd say two-three days would be perfect for the ideal city break.