Hit the Trail
If you like to hike, you don't have to give it up now. If you never were a hiker, this may be the time to start (but begin with short, easy trails). Stay out of constant sun (don't forget your baby's hat), and avoid trails with low branches. Use a front pack until your baby is too heavy for one and then switch to a backpack.
You can also just walk around town. Admire your neighbors' gardens and get to know the neighborhood pets by name. Don't limit your walks to balmy spring days. Try rain walks. If your baby is in a frontpack, sling, or backpack, an umbrella will protect both of you and your baby will be fascinated by the sound and smell of rain. Go out for an evening walk and bring a flashlight for extra baby entertainment.
What about parks and playgrounds? They're a great place to meet other moms, but save them for after your baby is sitting or crawling and can take advantage of the swings and sandbox. Until then, pick outings that interest you more; you'll be getting plenty of playground time over the next few years.
After your baby is able to hold up and control his head for extended periods of time (usually at around nine months), he's ready to experience life on a bike. Get a helmet that fits him well (make sure it has a gently rounded, not flared, back, or he won't be able to lean his head back comfortably) and a bike seat (make sure the seat keeps his feet away from the wheels) or a trailer.