Assuming you want to share them with the public and not just archive them as a backup, it's not a bad process once you get past the initial learning curve. Live Music Archive's FAQ is great and very detailed, so here's a general outline:
First you have to get your band accepted as a tradeable band. I believe this means that you have to send them an e-mail, outlining your trading policy.
Then you find the link called "upload", in the upper right. It'll direct you to the newish "Share" button, also in the upper right. (right where the Upload button was) That brings up a dialog box that will let you choose your files for upload.
You'll want to have your show chopped into tracks, converted to either FLAC or the other format whose name I forget - I use FLAC because it's easier for me and I don't have to worry about MD5 signatures or whatever. The program to convert it is suggested in LMA's FAQ.
Get the show cut into WAV Files and then compress them as FLACs. Be very careful with your file names because they will derail the whole thing if they're incorrect. They should be along the lines of
"Fen2010-08-14_D1T01_Hell_in_a_Bucket" etc. With "Fen" being an abbreviation of your band's name, 2010-08-14 being the date of the show, D1T01 standing for Disc 1, Track 01, and then the song's title.
Be careful not to include spaces or punctuation, they will derail your process. Also include a text file of your setlist.
Once it's all uploaded, click the link saying that you're uploading to the Live Music Archive. It'll ask you your band's name, the show date, and a unique identifier - which can be anything you want since the odds are there are no other copies of the show that you're uploading. That will bring you to the Metadata screen, which allows you to put in your band's name, show title, and song titles, among other info. It's a pain but then people can download MP3s and they'll flow right onto an iPod - very cool.
Once all that's done, it takes a while for the files to derive so it's streamable - 1/2 hour or so and anybody should be able to listen to them.
And just to show off now that I've typed all that...
Here's Fennario's main archive page, where you can reach all 31 shows that we have uploaded... not all were by me, but most of them were:
http://www.archive.org/details/Fennario
And here's the latest one. I'm pretty proud of the matrix mix I made on this one.. it's no 16-channel Vic Mix, but it's pretty clean and clear but still fat and juicy.
http://www.archive.org/details/Fennario ... he.Cannery