Will switching hosting companies or changing my IP address affect my listing in Google?

No! If done properly, switching hosting companies or IP address will NOT affect your Google ranking. Done properly means that there is no down time during the transition. If there is some down time then you could experience a temporary drop if the Googlebot just happened to come at that time. And, according the Murphy, it will. However, follow these steps suggested by Google and your transition should come off without a hitch: <--break->

1. Bring a copy of your site up at the new IP address.
2. Update your nameserver to point to the new IP address.
3. Once you see search engine spiders fetch pages from the new IP address (typically within 24-48 hours), it's safe to take down the copy of your site at the old IP address.