We have scanned a number of journals. The easiest way to do this would be to scan directly into Adobe Acrobat (the application, not the free reader) at black and white, 300 dots per inch. Then apply Acrobat's Capture feature to each file to make the files seachable and to reduce the file size.
You could use a regular office scanner, but it will take you some time. Basically, with scanners you pay for speed, but unless you need a scanner upgrade anyway or will be doing a lot of journals, you may not want to pay for a higher-end scanner. I strongly recommend sacrificing a run of issues by cutting the spines off them. This will make scanning a lot easier, particularly if you have a scanner with an Automatic Document Feeder (ADF). Even if you don't have an ADF, scanning unbound pages is still faster and more consistent than scanning bound journals.
We do this type of scanning on a cost-recovery basis, so if you'd rather have someone else take care of digitizing than doing it yourself, let me know.