Since the NBA is the only sport I've been following of late, my comments apply only to NBA playoff props. No idea what the books do for hockey and baseball.
I use 10 books right now. Here's what my books have been offering.
1. Carib. Surprisingly, they are the first to post as other books sit around waiting to copy Pinnacle and Olympic. They usually offer about 10 props per game. 30 cent line. $300 limit, but one can bet again after a money line auto-adjustment.
2. Pinnacle. They post their props in the early morning hours and are one of the few books to create their own. Typically, they offer about 10 player props plus some unique range of score type props. For example, for a 1st quarter, they might offer a "will the 1st quarter score land between x and y..." range type prop. They offer this for every quarter, the 1st half, and the game. They also offer a number of other adjusted-line type props. Offhand, I think they're using a 16 cent line for props -- can't recall for certain.
3. Olympic. They also post their props in the early morning hours. While they do offer a number of props, unfortunately, quite a few fall under the silly "will x's score land on an even or odd number?" category (or similar). A bunch of "first to do this..." type props as well. Overall though, still a good number of props offered. 30 cent line for the most part, though they are 'generous' enough to make the coin flip props 'only' 10 cents. $500 limits. Olympic's props were much better back when they would offer props on pts/rbds/asts/steals/mins/fouls on the top 6-7 players for every team. But perhaps they got beaten too badly on those.
4. WSEX. All I've been seeing is one player matchup prop per game. Disappointing for a book I otherwise really like.
5. Hollywood. They copy and post about 10 of Olympic's props mid-day. If a particular Olympic prop has seen one-sided action, Hollywood will adjust the number a bit. But the source of the props is quite evident. Think they've been using a 20 cent line.
6. Canbet. They post about 5-10 props mid-day. The sources appear to be Olympic and Pinnacle, sometimes slightly adjusted. 30 cent line to start but steeper than other books when the price rises (like all their offerings).
7. IIS. Another mid-day poster of about 10 props. Source appears to be Pinnacle with slight adjustments. Think they've been using a 20 cent line (even for reduced-vig accounts) -- can't recall for certain.
8. Intertops. Just a handful posted mid-day. Likeliest book to screw up a number. Limits are low, but I can't recall the exact amount.
9. Cascade. Like most, they post props mid-day. 30 cent line. $500 limit. Their props typically mirror Carib's. Since I doubt a book would use Carib as a source, best guess is that the two books get their props from a common source.
10. 5Dimes. By the end of the day, they will have many more props posted than anyone else. But that's just because they copy from a number of other books and lump them all together -- even some of Pinnacle's unique range of points props. The props can be hard to find on their site as they're posted in multiple spots. Most of them appear under "Conference Final Props", but a few are under NBA and NBA props. Think they've been using a 30 cent line. When they copy Pinnacle's props, they just pad some vig. They seem to start posting their props around mid-day but add to it as the day goes on as more sources become available.