Instead of using the built-in "Album" tag, create your own and use that instead. Go to: Tools --> Options --> Library. Click the Add button. Under General enter this information:
General
Name: MultiAlbum
Display: MultiAlbum
Category: Extended
Data
Data Type: List
Leave everything else alone and click OK.
Next, copy the data from your current "Album" field over to your new "MultiAlbum" field using MC's Move/Copy Fields tool. Click on Audio in the tree and make sure no panes are chosen (All is selected all the way across). Hit Control-A to select everything. Right-click and choose Library Tools --> Move/Copy Fields. Set:
Source: Album
Destination: MultiAlbum
Action: Copy (leaves source)
Hit OK.
Once this is done, you can either just use the new MultiAlbum field in all your View Schemes instead of Album (and add it to the Customize Current View dialog). The new MultiAlbum field will work like Keywords and will accept multiple entries (ether via drag-drop or semicolon delimited in the Edit Tag action window). You can also set the field to more than one "choice" when in Tag Mode and using the Panes to tag files.
But, you can even get more fancy if you want and make the new MultiAlbum field "masquerade" as the regular old Album field. First, edit the original "Album" field. Go back into Tools --> Options --> Library and select "Album". Click Edit and change Display from "Album" to "OrigAlbum". Click OK. Then, do the same thing for your new MultiAlbum field, and change it's Display to plain Old "Album". OK out of everything and restart MC. Once you've restarted it, in all the Add/Edit View Scheme dialogs and the Customize Current View dialogs (as well as details view) "Album" will really be a pointer to your new "secret" MultiAlbum field.
You might have to manually configure all of your existing View Schemes (under Step 1) to add in the new field (the old ones might still point at the old Album field, even if they don't say it)... I'm not sure because I've never done this exact procedure myself, but I've tested it briefly and it does work.
The bad thing about this procedure is that any portable media players (or other computers not using MC and the same library) won't recognize this new MultiAlbum field and will continue to show whatever happens to be in the old Original Album field. No biggie, and you can even probably figure out a way to autopopulate that field, but I don't know how...