What are 'brilliant' activities with manipulatives?

Preparatory questions and links:

Focusing questions:
What manipulatives do you consistently use?
What manipulatives have you introduced recently or that you would like to try soon?
Have you used online manipulatives? Which ones? Are they as effective as physical objects?
At what stage do you introduce or remove manipulatives - early stages, never, depends?
What areas of your curriculum would benefit from more activities, or work, with manipulatives, but it is difficult to introduce them?

(Provided by @ColinTGraham)

Threaded discussion from 5th August 2010 -
Threaded discussion from 9th August 2010 -

Links mentioned in the discussions, with contributor:
Math Manipulatives (provided by @cybraryman1)
National Library of Virtual Manipulatives (provided by @ColinTGraham)
Shodor Interactivate (provided by @mthman)
Lego Engineering (provided by @mthman)
Ramanujan Musuem and Math Education Centre - setting up a math lab (provided by @mathchat)
Math Manipulative Activites (provided by @mathchat)
Math Games and Puzzles (provided by @mthman)
Improving mathematics teaching by using manipulatives (provided by @mathchat)
Finger multiplication (for 5x6 up to 10x10) video explanation (provided by @MariaDroujkova)
Learning Mathematics with virtual manipulatives (provided by @ mathchat )
Binary system counting on fingers video explanation (provided by @MariaDroujkova)
How to use Chisanbop for basic addition and counting (provided by @mathchat)

Resources (costing money!) mentioned in the discussions, with contributor:
Algebra Tiles (suggested by @mthman)
Geoboards (suggested by @ccampbel14)
Cuisenaire rods (suggested by @ColinTGraham)
Lego red bucket (suggested by @ColinTGraham)
Two-colour poker chips (suggested by @math2go)

Other links which may be useful
Middle School portal for Mathematics and Science Teachers (age 11 - 15) (suggested by @mthman)
Almost every virtual online manipulative you ever wanted! A stunning applet! (suggested @ColinTGraham)