According to InformationWeek, Sony is offering $500 off of some laptop lines, in exchange for working Dells. You have to work through a Sony solutions provider, and unfortunately it looks like it’s only for the VAIO BX line:
Sony’s trade-in offer of $500 for working Dell systems eclipses the $300 it provides for trade-ins on all other systems for Vaio BX series notebooks. Sony said the rebate can be claimed by solution providers for their clients. Such a trade-in would represent a hefty discount off the price of some of the Vaio BX notebooks, which start at a street price of $1,171.
Would be nice if they offered this elsewhere in their lineup, or perhaps made it size-for-size – you trade in an ultraportable/12-inch Dell for $500 off a 13.3-inch or 11.1-inch Sony.