Well, the Japanese sales figures are available publically through
http://www.media-create.com and the total to date sales are tracked at
http://www.game-science.com
The US figures are tracked by
http://www.npdfunworld.com but not released publically so you'll have to wait for them to leak to various forums. I have saved the DS and PSP numbers for each month and they are as follows:
___---___---___-DS___PSP
Up to March: 1,650,895 618,000
April:___---___- 50,000 351,000
May:___---___--57,000 250,000
June:___---___112,000 294,000
July:___---___ 102,000 202,000
August:___---_103,000 167,000
September:__--164,000 146,000
October:-_--_--136,000 127,000
November:__---370,000 353,000
Total:___-___2,744,895 2,500,000
The DS was released in November 2004 while the PSP was released in March. If you want confirmations on individual numbers you can Google for example "NPD hardware November 2005 370,000 353,000" without the quotation marks. Here's also an image confirming the PSP sales up to September: (look at the bottom)
jay-t.com/public/gaf/npdoct.jpg
Sales figures for Europe and the rest of the world are harder to get but you can check out some UK sales here:
http://forum.pcvsconsole.com/viewthread.php?tid=17444
UK total as of December 17:
DS 846,000
PSP 668,600
Also, here's a chart tracking French sales for some recent weeks:
img2.kult-mag.com/photos/00/00/63/85/ME0000638547_2.jpg