That's the darndest thing about a pseudonymous digital currency. There's really hardly any actionable data.
There might be some trends you can recognize from these sources though:
- http://blockchain.info/charts
- http://bitcoinstatus.rowit.co.uk
- https://bitcointalk.org/index.php?action=stats
- http://stats.grok.se/en/latest90/Bitcoin
- http://blockchain.info/charts is very good, but I find it hard to understand adoption rate from it
- http://bitcoinstatus.rowit.co.uk is too depressing. I don't like it.
The last couple made it to my bitcoin bookmarks :-)
I'd love to have the wikipedia stats for a longer period than a month, something similar to the google trends