Recruiting the volunteers will be easy. Coming up with short-term, quick fix projects at nonprofits will be harder. Nonprofits have trouble identifying such projects at their own organizations, and mobilizing their own resources to support the volunteer in the project (the volunteer doesn't just walk in and start working without prep and support by staff). This list of tasks is great, but realize that it probably took a lot of phone calls, visits and hand-holding to help these nonprofits fully-define these projects and have them ready for a volunteer to walk in and do. So deal with that first, before recruitment. Here's an additional list of short-term assignments for tech volunteers.
Once you have the list of assignments ready for volunteers, then you can start recruiting. VolunteerMatch, Idealist, Craigslist, your local volunteer center, and your local newspaper will all get the word out, as well as making sure everyone on the onlne networks of your choice knows and are willing to pass on the word to their own network.
The Day of Service is great. Another great one-day tech-volunteer event are the Accessible Internet Rallies (AIR) events by Knowbility.