I use a square rubbermade container and pour from the corner (as if it were a spout). I make my dressings in the same container - add ingredients, snap on lid, and shake.
I used to have a tupperware shaker container ( which has a snap on lid and a snap on spout on the lid). I liked that it had a spout, but the square Rubbermade container is easier to clean.
I rarely buy jarred items but I have my dad save his glass jam jars for me. I put the ingredients into the jar and shake well. These are oil and vinegar style dressings. I wipe the rim with a paper towel after pouring to minimize goopage. They last for weeks. My fridge holds a nice cold temp.
I got a salad dressing cruet with mix by Good Seasons from the grocery store in the salad dressing isle. I just use the italian dressing mix with red wine vinegar and a little oil. I use it til I run out. If it goes bad, I haven't found out when that point would be yet.
Like some others, I use a rubbermaid/tupperware type of container and pour from the corners. I save and use glass jars from jams/preserves, mushrooms, olives, etc- all different sizes.
They sell medium sized mason jars at the dollar store near me so check that out if you'd like if you have that in your area.
Did you know that a pint size mason jar will fit on many blenders? Mine is an ancient Oster model, and I just put vinaigrette ingredients in the jar, screw on the blade, gasket and ring, then pop it on the blender base. It whizzes up great dressings! Then, I store it in the same jar. I've recently found that the plastic lids from PB2 jars fit on mason jars, so I use one of those.