It's no secret that TS3's Open-Neighborhood feature leaves a little to be desired (Unpopulated community lots, lack of a living-breathing city).

But reading threads like Show Us Your Shops, or even seeing other user's worlds, Sandy from Around The Sims, leads me to ask - what are somethings you do to your neighborhoods to make them feel more alive and more functional?

I've been wondering this myself. One of the things that really disappointed me when the base game came out was that there was this awesome playground by the school and I never once saw a single kid playing on it. I would see adults swing in the main park, but a lack of kids running around and climbing on stuff made me sad. Sometimes I wish there was some sort of mod where there was a "porchlight" type thing that would draw NPCs to the lot like moths.

This is kind of what I try and arm-bend my game into being. A virtual city / village. For that to happen, we need retail establishments. Most of my community lots are left blank if they are not a social bar or rabbit hole location. And that, three years into the game, is sad.
Sure I can build the odd aquarium, or cinema, but it's fake. I'm arm-bending the game into something it's not until we get retail, and it's mostly a fruitless excercise.
Sadly, I think most people who come on these forums are more interested in seeing werewolves (?) than to see things like coach drivers, amusement parks or cruise ships. People rarely ask for these things and it means the developers have little incentive to really make the towns come to life. Just give 'em a few new hairstyles, they'll be happy with that.
And alot of them are, unfortunately.

I kinda sorta gave up, and now I just play with the game as-is rather than trying to hammer a square peg into a round hole. The game is severely limited, and I don't see that changing.

In my game, sims usually attend community lots that have many different features for entertainment, like chess, darts, swings, grills, arcade games, etc... I try to fill comm. lots with them, to attract sims, but, to tell the truth, I'm not always successful. It's really bad that we can't have fully functioning restaurants, cinemas, various kinds of shops (EA, make Business EP finally !!!), and even normal parlors where you can sit on a chair and have your hair done, or get a pro make-up. It was in TS2, looked realistic, and I liked the animation when the hairdresser showed that little mirror to a sim for him to look at him/herself, and s/he would make a happy face, or cry in desperation, depending on whether the makeover was good or bad.
However, I must confess, in TS2 I had problems with visitors not showing up, too. It was rare to see more than 3-4 sims on a lot. In TS3 there are more sims hanging around, but still, it is so unnatural to see 5-6 sims in a big club, lol, it's like the party's over, but some drunk clubbers who lost the trek of time and of what's going on around, need to be reminded that the club's getting closed.

This is because lots with Schools on them are usually flagged as 'No visitors allowed' which means exactly that. If you'd change the lot flag into 'small park' or 'visitors allowed' sims would appear on the lot and play in the swings, etc.