Shopping list from H3 Tinker.it workshop Arduino & actuators by Alex Zivanovic and Brock Craft.

External power supply:

"Switch mode power supply" that offers six selectable output voltages (3, 4.5, 6, 7.5, 9, 12V), UK.
http://www.rapidonline.com/Electrical-Power/Power-Supplies/Bench-PSUs/3A-Switched-output-switch-mode-power-supply/65050/kw/ £13

Wiring:

"Stranded equipment wire" 22m, 2m of each colour
http://www.rapidonline.com/Cables-Connectors/Equipment-Wire/Equipment-Wire/Stranded-equipment-wire-packs/62318T
"Single core equipment wire pack"
http://www.rapidonline.com/Cables-Connectors/Equipment-Wire/Equipment-Wire/Single-core-equipment-wire-pack £1.60
Soldering iron set/ with Rapid model 212 digital multimeter, Antex XS25 mains powered iron with burn-proof silicone cable and fitted 13A plug; 2 spare soldering tips; a supply of solder; side-cutters; long-nose pliers; ESD-safe de-soldering pump: http://www.rapidonline.com/productinfo.aspx?clearance=1&tier1=Tools%2c+Fasteners £38

Multimeter (one is included in the set above already)
http://www.value-electrical.co.uk/

6mm pager/phone vibration motor
http://www.precisionmicrodrives.com/index.php?catTop=1
More about this device from fast-components
http://www.fastcomponents.co.uk/product_info.php?products_id=78&osCsid=47a28e103f7d1e55d4289df7511b543b

Cams, wheels, gears from Rapid:

http://www.rapidonline.com/products.aspx?tier1=Educational+Products&tier2=Graphics%2c+Art+%26+Design&tier3=Model+Accessories
Cam test set in pink
All kinds of cam wheels, gears, pulleys and fan blades also available at remtrak.uk.
Pricey but individual items: http://www.remtrak.com/robots/motors.htm (for 4mm shaft)

Solenoids and stepper motors:

http://uk.farnell.com/jsp/search/results.jsp?N=500005+1001538&Ntk=gensearch_001&Ntt=solenoid&Ntx=&isGoback=falseT

More solenoids at http://www.nsfcontrols.co.uk/Solenoids_Open_Frame.cfm but without pricing information.

Miniature solenoids
http://www.emessem-solenoid.co.uk/main/test_latching.htm

Interesting, but wrong voltage, 24V DC instead of 12V DC:
http://www.islikersolenoids.co.uk/Isliker-Solenoids-Products-Linear-Solenoids.html

13mm push action tubular solenoid,12Vdc:
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=4317526
(The question is if there is a spring holding the pin back so it doesn't fall out?)

A standard square affordable small push (high force) solenoid, 12Vdc/3W:
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0347652
347-652
LInk to a search at rs-online filtering "push" and "12V DC"
http://uk.rs-online.com/web/search

Miniature stepper-motors:

http://www.astrosyn.com/stepper.html

Miniature servo motors:

GWS Pico Standard Servo with JR/Hitec/Futaba connection There are smaller one's available such as the "Pico Servo Pico+ F BB."

Wind:

Probably any old DC 12V computer fan will do. Better 120mm diameter then 60mm.
Propellers (2 blade, 3 blade)
http://www.rapidonline.com/Educational-Products/Graphics-Art-Design/Materials/Propellers/66047
Fan, 60mm
http://www.rapidonline.com/Educational-Products/Graphics-Art-Design/Materials/Polythene-fan/71895
Cheap and silent DC 12V computer fan http://www.scan.co.uk/Product.aspx?WebProductID=784445, Speed cannot be controlled via PWM.

Sound & music:

Very inspiring collection of instruments, accessories and non-traditional sound sources:
http://www.knockonwood.co.uk/details.asp/percussion/423/buy/combi_bells.htm#
Shaker eggs at knockonwood: http://www.knockonwood.co.uk/details.asp/percussion/606/buy/egg_shaker.htm#T
Wooden xylophone: £16

More inspiring percussion devices at drumsforschools (a large range of "ethnic" instruments made from nuts or shells. Interesting could be their range of egg shakers in 5cm, 9cm and "giant": http://www.drumsforschools.co.uk/percussion-shakers-c-47_46.html

Water & sound

This could be interesting as it provides redundancy. Working with water provides a pleasant white-noise background which can be accentuated with (ambiguous) chime sounds. Additionally a solar pump could be used. Upon a visit the light increases providing more power to the pump ... and the IP addresses are played with solenoids.

A table-top sized Shishi-odoshi that fills and empties itself.
http://www.serenityhealth.com/bamboo_water_fountain-p-967.html

Solar water pump, not clear if the water-flow can be regulated.
http://www.taylorsgardenbuildings.co.uk/store/customer/product.php?productid=19356

Water bell fountain
http://www.serenityhealth.com/wtrbell.html
The idea is to hack this so the water-flow is provided by the solar pump above. Depending on the intensity of the light the water flow increases or decreases.
Solenoids can play IP addresses on the Woodstock chimes. This would allow redundancy (of the multi-modal media light and sound of water), ambiguity (as the bells will be ringing either as a result of the solenoids and of other causes).