If you want open source/community developed software, you can find them at talk.maemo.org, you can even ask questions or HOWTO tutorials from the community there.
However, if you want some gray area software, you should visit my homepage which hosts some very hard to find software for the N900. At the moment, it has the following:
- NeoPwn v2 (beta)
- Packet Injection (wifi) for N900
- Adobe Flash v10.1 for Maemo5
- VLC mobile v1.1.5 for Maemo5
If you have access to any other similar software which people cannot fine easily, do let me know and I'll host it as well.