Today there will be several demonstrations arranged in the center of Budapest, in the area of the Parlament, the Chain Bridge and the Heroes Square. There will be one gipsy demonstration, a group of motorbikers, a group demonstrating for bringing the peace back into the streets of Budapest, and one group will demonstrate against the current political leaders in Hungary (which is leftsided, led by Ferenc Gyurcsány). Hopefully everything will happen peacefully, but if you are around in the area, it might be that you want to take a turn to skip the biggest demonstrations. The demonstrations will be going on from around 14:00 and for some hours from there.
Two years ago the famous “Gyurcsány Ferench”-speach (Öszödi Beszéd) was published, and it led to major demonstrations and trouble in Hungary. Now, two years later people have still not forgotten about it, and that also has influence on the fact that so many demonstrations will take place today. You can read more about those protests and demonstrations in Wikipedia.