Funny you should ask. I just got back from the produce market on Hillsborough and 30th. I've been shopping for my produce there for years. It's been there for years. I read a book set in the 40's in Tampa and they referenced the market even back then.
There are booths and most sell the same stuff. You want to explore because some is more fresh than others, and since there's no a/c things wilt rather quickly. On the back row you'll find that things are priced a little less.
Things are based on $1. Just got 4 small green peppers for $1, 2 small red peppers for $1, a quart of tomatoes (6) for $1. Let's see...4 yellow squash for $1, 2 big green zucchini for $1, 2 eggplants for $1. Got a watermelon for $1 too. Hope it's still good. 3 pound bag of onions for $1.50, 5 lb bag of idaho potatoes for $2. 5 bananas for $1. I shop there for produce all the time. It's fairly close, about 12 minutes from my house, but even a longer drive is well worth it.
Also, when the season's right, you can get a bargain on some items. In season, I've bought tomatoes by the 25 lb box for $5. That's a lot of tomatoes, but they're in my freezer now, ready to make sauce.
If you want a novel experience and you're in the neighborhood and it's before 1:30 pm, you should check out Sanwa. It's a few blocks east of the produce market, on the same side of the street. It's international wholesale open to the public. They open at 3 in the morning and cater to the restaurant trade, but you can shop there too. If you've got a big family or are planning a party, it's a great place to go. They also carry some really unusual stuff. The owners are from the far east, so there's a large selection of eastern goods there.
If you're in east Hillsborough, there's 2 nice stands right off I-75 and Branch Forbes road. The one on the east side of the road has been there forever and I guess I'm loyal to it. The one on the west side of the road has only been there a year or so. Both are more expensive than the market at Hillsborough, but are still a lot less than you'll find at the grocery. In addition, the one I goes to features 4" pots for $ 0.25. 4 for $1. They'll have herbs and annuals. Again, they're not always the best and sometimes looked peaked, but if you're lucky enough to get there when the truck arrives, you can get some really good looking plants inexpensively.
I've been a stay at home mom for the past 10 years, so if you want to know anything else about how to make a dollar scream, I'm you're woman.