There are many outdoor activities that you can try out this spring in Austin that won't severely damage your wallet while getting you in the spring spirit.
Kayaking: I've always thought kayaking sounded scary. After all, you're strapped in to a small boat that if you flip over you have to flip yourself back with your own strength or you could drown. However, some kayaks are larger and seem more like a canoe, and if you happen to flip over, you will simply fall out and climb back in. Also, most of these kayaks won't flip over anyway because their use is usually only offered on relatively calm waters during certain touristy seasons. For instance, at the rowing dock, off of Zilker Park you can rent a kayak to explore Lady Bird Lake. Paddle boats and canoes are also available to rent. The cost of borrowing a kayak is only $15 an hour.
Very friendly swan who's convinced we have food
This is a lot of fun for those who are just looking for a good time and not necessarily an intense sport. It does involve a lot of paddling, and birds will follow you hoping for food. I suggest bringing some bread in case you have a run in with a swan. They're very friendly and overly-friendly if they think you have food. In fact, I've heard of swans being aggressive to the point of attacking. So maybe don't make them angry. You could also just raise a paddle whenever they approach. Seems to be effective. They're pretty though.
Driving Range: Another good spring outdoor activity is going to the driving range. This is perfect for those who aren't golfers yet or who can't afford to join a country club or pay for an individual golf session. Most driving ranges charge a little over $10 for a large bucket of balls that can keep you busy for an hour or two. This is also convenient because it's not as time-consuming as playing 18 holes, so it'll easily fit in to your schedule when you want to do something outdoorsy but don't have a ton of time.
Hard Drive Golf Practice Range in Round Rock, TX
Disc Golf: An absolutely free outdoor activity is playing disc golf (after you buy some discs, that is, which are cheap). There are ranges all over Texas that have 9 to 18 holes, and it's a fairly low-stress game that involves throwing a special Frisbee-like "disc" toward a goal. Other than that it basically follows the same rules as golf. Though you occasionally loose discs in woods or streams, it's a slightly easier game than golf, and doesn't take quite as much time. There are disc golf courses all over Austin. The best are located at Zilker, Pease, and Metro Park (Circle C) on Slaughter Lane, the latter being where the below picture was taken.