when i am on a wireless network can someone access my laptop or see what i am doing online, such as financials

Only if your wireless connection is not secured....

The best things to do to protect yourself from vulnerabilities are:

1. Ensure that your connection through your wireless is encrypted (many wireless routers support this)

2. Install a firewall onto your laptop.

3. Configure and mask all your IP address.

all depends if you are on an unsecured network or not. if not, then it is possible. On itunes, I have listened to other peoples music while connected to their unsecured networks. First thing you should do is to put your network on WPA security, or if your router doesn't have it, then WEP(though it won't be as secure). Also, set the router so it doesn't broadcast your ssid. If you do those two things you should be reasonably secure.

Only if they have your IP address, you do not have a firewall, and it is an open network.

don't know only if someone can access your feed if it is and protected

Yes ....if it is worth their time, thay sure can get it done.