Try to practice for the U.S. WPF Sudoku Grand Prix!
In the Sudokucup Daily League the following variants are prepared for you:
20.05.2013 - Consecutive Sudoku
21.05.2013 - Arrow Sudoku
22.05.2013 - Thermo Sudoku
23.05.2013 - Dynasty Sudoku
24.05.2013 - Property Sudoku
25.05.2013 - Jigsaw Sudoku
26.05.2013 - Killer Sudoku
http://sudokucup.com/node/1901?typ=varianty