We have the Edushape Edu-Tiles 36 Piece 6x6ft Play Mat. We put it out right around the time our first baby started crawling. It provided a softer place for her to fall over as she developed her gross motor skills and is reasonably comfortable for adults to sit or lie on while playing at eye level or being climbed over. They can be especially helpful if the adult has bad knees or is pregnant.
In particular we picked this brand over something like Skip Hop Zoo Playspot because we liked that the tiles fit together without additional extra pieces, which would just get lost with time in all likelihood. Moreover, this flexibility allowed us to split the one mat between the living room and her room, given that neither space was big enough to support an entire mat all its own.
In addition to being soft and colorful, it also let our daughter basically teach herself letters and numbers and taught her about putting together puzzles!
Finally, this is a great item to register for - you won't need it right away, but probably faster than you can say "grow".