My 2.5 year old DD is very into:
Her play kitchen (a favorite of kids of all ages that come to our house) - we have a nice Waldorf style kitchen and lots of accesories. Her favorite accessories are a pizza (like the one by Melissa and Doug), a sushi set (by Melissa and Doug), plates, bowls, and cups for serving everyone (ours are mostly by Plan Toys), and the pots and pans we got for nothing at Ikea (that are nice stainless steel ones much like my pots only tiny).
Her doll house - It's a nice Waldorf style one full of wooden furniture (mostly the Guidecraft set which was very reasonably priced and rather well made) and nice Evi dolls. It's amazing the stories she makes up with it. At play groups there are often 2-4 boys about her age playing with it. We've had several older kids more like 8-12 years old sit and play with this for a LONG time too.
Her basket of musical instruments (probably the most popular item at play groups) - Drums, maracas, sand blocks, rhythm sticks, zylophone, a triangle, etc.
This was a great starter set that we got for her first birthday. She loves her
treeblocks music wand
that makes a nice ring when you tap it against anything. It gets so much play that I've considered ordering a collection of shapes.
Blocks - we have some basic cube blocks (an alphabet set and a nursery rhyme set), but the favorites are the more unusual one. We

the Speil and Holz nesting sets (we have all of the elements as well as the flower and both color sets of nesting bowls). We also have a few other Speil and Holz block type items that are stacking (a double rainbow, a pyramid, and a flame). All of this gets plenty of play. The
little set of bowls is probably her favorite.
Puzzles - Her current favorites are the
beginner pattern blocks by Melissa and Doug and a puzzle with multiple faces/bodies/legs like
this
.
Small animals and dolls - Schleich animals (plastic, but awesome detailing), the 5 Monkey finger puppets that go with the book "5 Little Monkeys Jumping on the Bed", little gnomes like
these, etc. These take on all sorts of roles all over the house, get carried around, put to bed, fed in her kitchen, act out stories, and on and on. It's also very easy to stick a few in the diaper bag or the car seat when we're out and about.
Dolls and stuffed animals - Once again for lots of roll playing - putting them to bed, reading them stories, pushing them in her doll stroller, wearing them in slings, etc.
Dress up stuff and BAGS - sunglasses, play silks, necklaces, headbands (with bunny ears, etc), purses, bags, bucket, backpacks (anything she can pack up and carry around).
Books - She's currently very into nursery rhymes and we're checking out a new Mother Goose book each time we go to the library. We do lots of reading.
Outside she absolutely loves her swing set (ladder, slide, rock wall, swings, etc) and her "rock box" (a sandbox filled with pea gravel). She's very into climbing and I think for her third birthday we're going to get her a dome climber type thing.