|Queen Anne's Lace
Queen Anne's Lace is similar to Common Yarrow, but it is a bit larger. Like Common Yarrow, the flowers form a flat cluster at the top of the plant. Queen Anne's Lace gets taller than Yarrow though, and its leaves, though fern-like, are not as feathery as Yarrow's.
If you find some, and if it's OK to do so, pull one up (most people consider it a weed, so it's probably OK, but you really should check first). Now smell the root. Does it smell like carrots? If so, don't be surprised - another name for Queen Anne's Lace is Wild Carrots! Now check the underside of the flower. You should see some leaf-like bracts coming our from the stem just beneath the flower cluster. These should have three forks. If you cannot find three forks, you may have found Spotted Water Hemlock instead, and that plant is very poisonous.