The Government of the City of Buenos Aires has several live webcams located in different places of the city. The images are updated each 30 seconds, and you can see the date and the time when the image was shooted in the lower right corner, as you can see in the example here on the right.
Image: 10/04/2007 21:33:09 (9:33 p.m.)
Choose the location you want to see and click on the corresponding button on the left. You will be linked to the proper webcam.