I love my roombas, I have one on each floor. They don't take the place of a regular run of the vacuum, but they do make it a once a week thing instead of a once every other day. But after 5 to 8 runs, the roomba filters are pretty much shot and even blowing them out doesn't restore them back to brand new. You can of course buy replacement filters, but they cost in the neighborhood of $12 a piece for the aerovac variety. This is a 5 minute solution that will let you refurbish your roomba filters for about 12 cents a pop and gain a fair bit of performance out of the deal. You'll need
A straight screwdriver
an exacto knife or razor
some 4 x 12 register vent filters (12 of them at home depot for $4)
and of course an aerovac style roomba
The Freakduino-chibi is of course optional.
Step 1: Removing the old filter material
Removing the old filter material isn't difficult, but you have to be careful that you don't break the plastic. Using a razor, first cut the tops and bottoms of each exposed filter element. Next cut the bottom of the edge filter elements on either side.
Step 2: Removing the old material part 2
Pull the old material out of the spaces, being careful not to break the plastic. The material will tear and you'll probably have to spend some time cleaning it out. Once you are done, you should have a clean(ish) filter basket.