I have a WiFi network at home and a couple of laptops.
I understand that there are some external backup drives that slowly back up data over WiFi, and run in the background on the laptops.
Have you tried any of these?
Which one worked for you?
Which one is the best (in terms of cost, reliability, usability)?
FYI, this is for Windows XP and Vista (no Macs in the house [yet])
I use Iron Mountain Connected Backup. It backs things up to their servers. This has the advantage of protecting the data in case of something, like fire or theft, that could result in the loss of both your data and your backup.
I am a big fan of mozy myself mozy.com
you also may want to look into allways sync. it can be set to backup to shared folders on other computers on the network, wired or wireless does not matter.
Any more non-online options?
I’m a bit paranoid about backing up some of my personal data (financial, taxes, etc) onto online accounts.
Don’t be, all of the stuff is HIPPA compliant, data is stored encrypted, etc. the allways sync option I mentioned is for backing up to other computers on your network, meaning no exposure to the outside world.
Can there be any legal issues with online backup?
That is, is there some document that, if I have on my laptop in my home, it is fine, but if I back it up online, on some company’s server in another state, I may be violating some law?
Simple example would be pornography, but that’s not what I had in mind. Any other classes of documents which would have this issue?
Maybe a document from a company with which I signed an NDA agreement?
If I back up the document to an online server, can the company sue me for “disseminating” information about their company?
I am not aware of any issues with data being stored in other states, if you are in an area prone to hurricans and such I would think it was prudent.
Generally speaking, no. Utilizing the 448 bit encryption they provide with the software you have made a reasonable effort to protect that data in the eyes of the law as I understand it (IANAL, just a computer guy)
Am I reading that right? MozyPro is under $5 a month?
That sounds right. I use Carbonite myself, and it’s $55/year, or cheaper for more years.
It takes about a week to get the initial backup done, and then just updates on the fly when your system changes. You can manage your own encryption key if you like, and everything is encrypted before being sent to their servers. Restoring files is easy (I’ve done it), and after losing 2 laptops to mishaps, I love not having a locally stored set of my data to maintain.
FYI, I started another thread to address the legal question (since I don’t think SDMB lawyers are very likely to read this thread)
Simplest way to do it is get a utility like Acronis TrueImage and use a WD Passport drive. The Passports are laptop hard drives in a small external case, powered by the USB cable.
Mozy home is, a basic mozy pro account ends up being like $7-$8/machine. The pro side accounts are not unlimited, its like $0.50 per GB after a $5/month basic charge per machine. Pro accounts are cool in that multiple machines can share the same backup space and can be individually assigned X amount of space if desired so a soon to be ex employee doesent download a ton of movies and wipe out the space being used for mission critical application backups.
Image backups are cool and all but still need to be run manually in most cases.
Since mozy home accounts are unlimited space, you can image your hard drive every week, save it locally so the mozy account grabs it, and have a full image restore there too 
Acronis Scheduler. I usually schedule incremental backups for Sunday through Thursday, and full Backups for Friday and Saturday. I swap backup drives Friday after the full backup runs.
Personally I don’t trust a backup system that depends on thousands of miles of continuous wire, and I don’t trust my data on somebody else’s server.
If these are Windows boxes, get yourself a box running Windows Home Server. It will back up everything every night.
I just took a look, and it looks good. Does it do the backup over WiFi, or do computers need to plug in to be backed up?
WHS demands a wired connection for itself, but as long as clients have some sort of TCP connection, the rest really doesn’t matter.
Wired connection to your WiFi router?
Correct. Note that the demand is in the documentation: I’ve not tried it on a pure wireless connection.