This upcoming weekend the 405 Freeway will be closed from Interstate 10 to 101, many of the local news stations are referring to it as Carmageddon. Some of the on/off ramps may start to close as early as 7pm on Friday and will be closed completely by midnight. Lanes are expected to reopen 5am Monday morning. This should have a minimal impact on Disneyland as it is almost 50 miles from the park, but if you were planning on visiting Beverly Hills, the Getty Center, or other places in the area expect to find major delays and traffic. This also means people will be re-routed to other freeways so expect more crowding there, and this could effect the I-5 since people traveling to/from the North/West will not have the 405 option and will be forced onto the I-5 to head into Orange County and down toward San Diego. Also note there is an ongoing project on PCH north of Santa Monica that effects Southbound lanes.
For more information on the project here is the official Caltrans website: http://www.metro.net/projects/I-405