They appear to be transactions where forrestv consolidated a zillion small inputs into a single larger output (to make them easier to spend in the future).
FYI, if you are writing code to find p2pool blocks, I found that it was much easier to get data from blockchain.info' API in json format than to try to screen scrape the HTML from blockexplorer.
p2pool.info's logic for finding p2pool blocks is:
1. Looks at every
new block as it is found and examines the generation transaction and see if a) it has the donation address, b) has the weird script at the end, and c) has at least 25 outputs (this filters out p2pool forks that have only a few people mining on them)
2. Every once in a while looks at
all of the transactions for the donation address looking for generation transactions that it doesn't already know about (because they came in way late and are probably orphans.
I may have to look at that. But in the meantime, I have the scraping done and now have an Android app that notifies when a p2pool block is found (assuming logic is correct) and is set up to be able to report mining hashrate (cause I just like to know). Now I just need to work together some of the glue code and tidy up the graphics a little and I'll release it on here.