These images are also here:

http://sudokuvariants.blogspot.com/ ]

The names are merely descriptive. I don't know what they may actually be named. They are all from Japanese magazines 5 to 10 years old.

Irregular groups.

Very common variant. Sub-groups are irregular instead of 3x3 boxes. These irregular groups may or may not be symmetrical.

Disjoint groups

In addition to the standard 27 groups (rows, columns, boxes), there are 9 more "disjoint" groups, each shaded on of 9 colors. All digits on one color must be different.

Diagonals

The two main diagonals must also contain each digit.

Extra groups

In addition to the standard 27 groups (rows, columns, boxes), there are 4 more groups, shown with shading. The number of auxillary groups varies.

Even and Odd

Dark shaded cells will have even numbers, light will have odd.

Overlapping plus diagonal groups

These overlapping puzzles include diagonal groups -- the 4 main diagonals must have one of each digit.

Overlapping

A variation from the standard overlapping puzzle

Overlapping

A variation from the standard overlapping puzzle. Cells marked with squares are not used in solving, only for sending in solution. Purpose for STAR cell is unknow. I'm guessing it's a hint -- either something like START HERE -- or possible there is an actual clue somewhere in the magazine. I don't know; I don't speak Japanese.

Three overlapping -- tight

Four Overlapping, standard

Again, don't know what the star is for. You can ignore the four square marks in cells.

Four overlapping variation

A variation of the standard 4 overlapping puzzle

Five overlapping, standard

Seventeen overlapping 9x9 puzzles

25x25

Notice the English word TEN is embedded in the pattern and it's not quite symmetrcial.