Type to use for "Status" columns in a sql table

I would go with number 4, but I'd use a char(x) column. If you're worried about performance, a char(4) takes up as much space (and, or so one would think, disk i/o, bandwidth, and processing time) as an int, which also takes 4 bytes to store. If you're really worried about performance, make it a char(2) or even char(1).

Don't think of it as "meaningful data", think of it as an abbreviation of the natural key. Yes, the data has meaning, but as you've noticed that can be a good thing when working with the data--it means you don't always have to join (even if to a trivially small table) to extract meaning from the database. And of course the foreign key constraint ensures that the data is valid, since it must be in the lookup table. (This can be done with CHECK constraints as well, but Lookup tables are generally easier to manage and maintain over time.)

The downside is that you can get caught up with trying to find meaning. char(1) has a strong appeal, but if you get to ten or more values, it can get hard to come up with good meaningful values. Less of a problem with char(4), but still a possible issue. Another downside: if the data is likely to change, then yes, your meaningful data ("PEND" = "Pending Authorization") can lose its meaning ("PEND" = "Forward to home office for initial approval"). That's a poor example; if codes like that do change, you're probably much better off refactoring your system to reflect the change in business rules. I guess my point should be, if it's a user-entered lookup value, surrogate keys (integers) will be your friend, but if they're internally defined and maintained you should definitely consider more human-friendly values. That, or you'll need post-em notes on your monitor to remind you what the heck Status = 31 is supposed to mean. (I've got three on mine, and the stickum wears out every few months. Talk about cost to maintain...)

Go with number 3. Create a view that join's in the status value if you want something inspectable.

I would use an INT, and create a foreign key relationship to the status table. An INT should definitely be safe for an enumerated status column.