Stack & Whack and OBW's are both types of kaleidoscope blocks. S&W blocks can vary in looks and form and are set with sashing in between the blocks. More than one fabric is used in the blocks. S&W is the term coined by Bethany Reynolds in her book. OBW blocks are all made identically from one fabric. It is the way the fabric is cut that makes the kaleidoscope variations. OBW blocks are sewn together without sashing. OBW is the term coined bt Maxine Rosenthal in her book.

K3n explains it very well in the intro to the Topic List "One Block Wonders, Kaleidoscopes, etc, here

http://www.quiltingboard.com/virtual_section_list.jsp

the difference is who is making it...which book they are using. different people designed quilts using a specific technique...and called it what they thought was a good name...there are differences...a stack and wack you stack up layers of fabric cut it all together, rearrange the pieces and re-sew them...so stack & wacks are not always kaleidoscopes...
one block wonders and kaleidoscopes are pretty much the same; some times (depending on the pattern you have) the one block wonders are put together ...one block at a time...where as (some kaleidoscopes) are constructed in rows instead of in individual blocks

Hexagon OBW are sewn into half hex's first, then pin the two halves together when you lay out your design for the top. After all is arranged, then you sew the half hexs into rows. When the rows get sewn together then the whole hexagon appears. The hexs nest together, staggered across the whole top, usually clumping same colors together. Octagon OBWs get made into a square blocks, adding those little triangles onto the corners. Then when all the blocks are sewn into rows and the rows together those little triangles make a square inbetween the oct's. OBWs can be made with different fabrics in the same quilt top, but usually are from one fabric print.

thanks to all... i'd been wondering about this, too.

Kaledioscope quilts is the generic term for ALL of these types of quilt.

Stack n whack is a term coined by (and trade mark owned by) Bethany Reynolds. Her technique typically includes sashing between the blocks. She uses many forms of kaleidoscope - squares, hexagons, octogans, fans, strips etc.

One Block Wonder is the term (not trademarked) used by Maxine Rosenthal to describe her version of kaleidoscope quilts made from EITHER hexagons OR octogans where the individual blocks are set together WITHOUT sashing to create an overall design.

There are also kaleidoscope quilt designs that don't use a layered stack of identical pattern repeats, traditional block designs, usually octogans, using several different fabrics to create the 8 wedges that make up the block.

There is a also the technique called Kool Kaleidoscopes by Ricky Tims that uses templates cut from strip sets sewn together to create unique designs.

Check out the link Katrine posted for more information. :-D