You might not have time for this, but might know a nice nanna who can knit you up some small squares in various textures. These are so versatile and will last forever. They start out just feeling nice, then end up being peek-a-boo tools, then dolly blankets, then dinner plates, or makeup. They really stimulate the imagination.

Go to a local op shop and look for suitable coaster sets, which encourage a lot of pre-mathematical learning. Napkin rings, tied together on a ribbon make lovely sounds and are fun to explore.
Silk scarves, if you can get them cheaply.
Bits of wooden stuff. I have found heaps, no idea what they were originally for, but fun to explore, and later find use for them as pencil/paper holders, dolls' houses etc.

If you sew at all, or know someone who does, get some recycled materials and sew them up in a little tulle bag (orange and onion bags work, you just have to sew them up.) Things I have put in are: milk bottle tops, crunchy paper, corks, teaspoons, bubble wrap. Possibilities are endless. The tulle bag stops them from swallowing items, but they still get to explore them. And then you can just dunk them in hot soapy water to clean them.

Photo shops will often give you film canisters. Fill these with various things and glue the lids on. Ideas are: kidney beans, salt, sprinkles, marbles.

Finger and hand pupets are another toy that will last the test of time. Go for the fabric ones, really sturdily made ones, because they will love them up to and beyond 10 y.o.a.

Wooden blocks, if you buy a good set they will love them forever. Great for reaching for/sucking on now, knocking over in 6 months time, stacking later on and constructing further down the track.

As a PP mentioned, bottles with "stuff" in them are great, try also a combo of baby/vegetable oil and water with food colouring, or coloured water with detergent in it, or plain water with bits of cut up drinking straws in it. Glue the lid on, and you're away. Again, these can be really versatile. When I worked with under 2s I always had some of these around and kids do some really creative things with them.

So, um, that should keep you busy for the next year or so! I believe so much in using everyday items with babies; there's probably plenty more ideas to come