Serious Eats - seriouseats.com

As I've grown suspicious of plastics, I've started using these to bring my lunch to work. I find they're much easier to clean than Gladware and less likely to leak.

Mr. Boyfriend has just moved in and is looking for work. Due to this we're doing quite a bit of economy cooking, and I think I'm eating better even though we're spending less. I've cut out a lot of processed stuff, and we're eating simple roasts that provide lots of leftovers.

@Kerosena: For what it's worth, I've nuked Mason jars (without their metal rings or lids) in the past with no repurcussions.

According to the FDA you should only use vessels labeled as safe for microwave use.

Less conservatively, a Michigan State University page I found provided the following guidelines for determining the microwave safety of a glass vessel: Microwave the empty container for one minute. It's unsafe for the microwave if it's warm; it's OK for reheating if it's lukewarm; and it's OK for actual cooking if it's cool.

You can read more from both points of view here:
http://www.foodsafety.gov/~fsg/fs-mwave.html
http://web1.msue.msu.edu/imp/mod02/01500615.html

As an aside, several other websites I found pointed to the benefits of using microwave-proof glass or ceramics for microwaving, especially for fatty foods, in order to avoid the possibility of the migration of toxic constituents from plastics to food during heating.

I grew up on a farm where Mason jars were reserved just for canning and used everywhere, particularly the wood shop. If you attach the lid to a surface, you can unscrew the jars and fill them with nails, tacks, screws and so on. My friend used one as the cover for his light bulb in his very beautiful sandstone tiled shower. It looks clean and clever and does not detract from the overall design. From year to year, I replace the lid linings but not the screw caps - these are good for years as long as, after you eat the jar's food contents, you wash and dry them. I can's imagine using a plastic lid - seems antithetical to the jar's purpose.

@Maureen: I'd say Mason jars definitely beat plastic containers for storing spices. Glass has little or no permeability, but some/most plastics have quite a bit (which is why plastic containers tend to stain and hold on to flavors and aromas, despite washing and soaking). Mason lids in good condition also seal very well - in my experience far better and more reliably than most plastic storage containers - keeping contents fresh. The one thing to keep in mind with spice storage, no matter how airtight or impermeable, is that spices are light sensitive and should be stored away from direct light sources (e.g. in a cabinet or closet), particularly if they're being stored in clear glass or plastic containers that provide little protection from light degradation.

I use these for so many things, I make sure I keep a box each of the Wide Mouth quart, pint and 8 oz in my pantry. I store my different salts in them, dressings, marinara for freezing, canning jams & jellies, storage in my shop in the garage..just about everything!

The other weekend I even used the large metal rings as molding forms for a recipe!

I buy my mason jars at the local 5 & 10 store. I shudder as I type, but I've also seen 'em in Wal Mart. For those of you wondering about lids, you just need the metal rings (these are reusable) and the metal discs (these are SINGLE USE only if you want the jar completely air-tight). I also have seen plastic lids, but you cannot use these for canning as they do not seal 100%.