Searching for patents
Finding equivalent patents from other patent offices
If you have a patent from one patent office, and you want to search for that same patent in the database of a second patent office, a good method is to look for the inventor(s) of the patent and search the second database for patents which list that person. If there are multiple patents in the second database which list that person as an inventor, then the patent names will usually be similar enough that you can guess which patent is the equivalent.
Searching for inventors' names is more reliable than searching for patent names/titles because those often change slightly to comply with the requirements or categorisation of each particular patent office.
European Patent Office
This is a good EPO patent search engine:
(Possibly out of date instruction: For example, to find granted patents, put "epb" in the "Publication number" field.)
- http://www.patentdebate.com/PATAPP/ (March 20th 2009, not working, try again in a few days)
- And there is something called Depatisnet with a website in German. I hope a German-speaker can look into this: 
As described by Benjamin Henrion in September 2012:
Here are the recent EPO software patents granted:
You should tick only B documents (granted patents)
If you search for IPC symbol G06F9/44 (for "Arrangements for executing specific programmes"), you will get 50 software patents for 2012.
If you search for IPC symbol G06Q (for "Data processing systems or methods, specially adapted for administrative, commercial, financial, managerial, supervisory or forecasting purposes"), you'll get 100 business method patents for 2012.
- EP0811911: Computer system and method for executing network mobile code with reduced run-time memory space requirements
- EP0824236: Selective download of applets
- EP1343082: System boot using nand flash memory and method thereof
- EP1307024: A distributed computer system
- EP1280056: Generation of debugging information
For the USPTO...
Using Google Patent Search
Google Patent Search only covers US patents.
Here's the homepage:
As well as searching for a patent based on the patent number, you can use special parameters such as "inassignee:NAME" to search for patents assigned to NAME. For example, to find patents assigned to Tandberg Telecom AS, you'd put this in the search box:
inassignee:"Tandberg telecom as"
And you'd get these results:
Note: This will not find all patents owned by the named company. The company might also have patents but have them assigned to another entity, or have them assigned to the company founders, or the company name might have been different at time of filing.