Need Suggestion Common Parts for Arduino Projects

I would skip the 74LS47 and go with shift registers that can drive LEDs directly, like TI's tpic6b595 open drain shift register. Can drive columns of LEDs if needed, or single segments of 7-segment displays. The 74LS47 offers no storage capability, so you have to put the data into something for it to decode anyway. Why not go direct? Then you also have the capability to do more than just 0-9 and odd shapes it uses for ABCDEF - you can define your own A, b, c, d, E, F and L, P, r, h, g, J, etc.
I've also been using a good old octal latch like the 74F374 as shift register, display flickers a little while loading, but it suffices for my needs.
Did you hve shift-in registers listed too?
I would get extra on the LED current limit resistors too.
Pushbutton switches. 3x4, 4x4 Keypad. (can get a 4x5 for $1 from http://www.surplussales.com in Nebraska!)
Depending on how big your project gets, wirewrapping could be considered vs point to point soldering too. wirewrap sockets are nice to build with.
http://www.marcospecialties.com/product.asp?ic=SIP20L
Some generic diodes like 1N4007.
If you are driving lots of digits, then some multiplex control chips from MAXIM are also nice, like the MAX7221 to control 8 digits via SPI interface.
I wouldn't worry too much about general parts - get parts for a specific project, but get a few extra each time.
I would also recommend an oscilloscope, such as the $89 kit from www.dpscope.com, or download a soundcard scope like Virtual Analyzer. Good for checking out things like PWM, often times a multimeter just can't show you what's really going on.
And a couple of boxes to mount things in. I have been using Really Useful Boxes (found at Staples, Office Max, online). Pretty low cost, easy to drill for mounting connectors & stuff.
Also a couple pieces of "island of holes" PCB like velleman ECS1/2 for building up on after getting things working on solderless breadboard.