We cleared out a kitchen cabinet for DD, which she seems to like. She has some cleaning supply type things in there (her own dust pan & brush, a sprayer & rag, etc), and I rotate activities in there, too. Right now she has a little box with her scissors and some paper scraps (she loves cutting paper!), a beading activity (pipe cleaners & wooden beads) and a matching activity ( glued some cut out shapes onto cards, in different patterns, and she selects other cut outs to match them).
Other things that rotate in include sorting activities (e.g., different colored pom-poms that get placed into an egg-holder that have the bottoms colored to indicate which goes where), pouring (small measuring cups/pitchers with rice or beans - though only as much as I'm willing to have her spread everywhere!). I bought a cheap water-proof table cloth, and she is pretty good about putting that out for her activities, so even if she does make a mess, the clean-up generally isn't that bad (and most of the time I can get her to help).
We also have a small tub (a plastic "drink tub" I found at bed bath & beyond) that she just fits in & I can put pretty much anywhere, so she can play in the water while I do things in the kitchen, take it outside while doing yard work, etc. She LOVES "swimming." I will sometimes put a bucket/pot next to her, and then she will use a cup to pour water into it.
Another of her favorite activities is putting away her clothes. I put labels on her drawers (a picture and the word) so she knows what goes where, and just give her one thing at a time (and don't worry about whether it's folded, lol).
For mixing/stirring - DD wanted to stir something, and I wasn't sure what to give her (flour seemed too messy), but I happened to have an expired bag of ground flax seed which was perfect! Still can get messy if she starts wanting to pour it (she mixes it with water), but it's heavy enough that she has to try, KWIM? I wouldn't buy it specifically for that, but if I found some super-cheap nuts, I could probably get the same consistency in the food processor (we still have some of the flax left, so I haven't actually tried it, just an idea). Actually, acorns might work, too, and DD loves going out and hunting for things. Hmm...
Hopefully that will give you some ideas (and looking forward to hearing more about what others do)!