Let me just start by saying that I do not particularly care for infant car seats. They certainly have their place, but I hate seeing babies stuck in those things for long periods of time outside of the car. More on that later.
There are a few good options when it comes to infant car seats.
Graco Snugride: If you are going to purchase this seat, make sure that the straps can be adjusted from the front. We had a rear adjusting snugride and it was very difficult to get the straps how they need to be. The snugride is not the easiest infant seat to install and you may need to use a pool noodle to get the proper 45 degree recline. Snugrides are good for infants 5-22 lbs and less than 29 inches tall. This seat will last anywhere from 4-8 months, although that depends greatly on the the build of your baby. My babies were 22 lbs by 4 months. Compatible with all of the Graco strollers and many other strollers.
Graco Safeseat: Safeseats are generally easier to install than snugrides and last many people a year due to the higher weight limit. Safeseats are for infants 5-30 lbs and up to 32 inches tall. Compatible with all of the Graco strollers and several other strollers.
Chicco KeyFit 30: KeyFits are highly recommended on all of the car seat boards. They are for babies 5-30 lbs. I can't find the height limit, but I imagine it's similar to the Safeseat. Easy to install. Compatible with the Chicco (pronounced "key-co", by the way) strollers and some others.
Yes, there are other infant seat options on the market. However, these are the three that are most recommended. For what it's worth, we will be purchasing a Chicco KeyFit for baby #3. I really like the higher weight limit and since our baby will only be three months by the time winter is here, it will be nice to get the baby bundled and buckled in the house.