Site Collection

50,000 per website

Sub site

2000 per top level site collection

Documents

10 million per document library

This is a very arguable limit. This depends on the document size, and what specifically are you doing with the document. For instance, if you are checking-in, out and versioning – this limit is a lot lower.

Also, no view must return more than 2000 documents unless you create logical indexes on certain columns, in which case you can go to about 20,000 documents per view.

Items

2000 per view

As mentioned above, no view must return more than 2000 documents unless you create logical indexes on certain columns, in which case you can go to about 20,000 documents per view. This limit is common to lists and document libraries.

Document File Size

50MB recommended, no more than 2Gb ever.

Anything greater than 2GB will error out. Anything greater than 50MB will severely negatively impact your database performance. Larger artifacts should be stored in a separate site in a separate content database on a separate spindle in the database server.

Lists

No more than 2000 lists per site

In this case, Lists = Lists + document libraries. If you have 2000 of these in one site, the navigation will become extremely clumsy, so in most cases you wouldn’t hit this limit.

Field Type

256 per list

No more than 256 fields in a list should be used. Crossing this limit causes severe performance degradation. Instead, you should use linked fields instead.

Web Parts

50 per page

This is again a very arguable limit. SharePoint webparts out of the box unfortunately do not support asynchronous loading. It is possible to introduce this behavior by modifying the aspx page, but it requires developer intervention. You will note that page load times increase exponentially as the number of webparts on a page increase. This also depends on the complexity of the webpart. You should leverage AJAX for pages with a lot of webparts.

Users

No more than 2 million per website

Also  note, if the profile import of a user is too wide, this limit significantly affects both the shared service provider database, and the content database.

Number of SSPs in a farm

No more than 20. Recommended maximum = 3.

Number of websites per SSP

99

Number of sites per content DB

Less than 50,000

Number of content databases

100 per web application.

Number of search indexes

No more than 20 per farm, no more than one per SSP.

Index propagation becomes horribly complex as a large number of SSPs are added. To avoid this scenario, you should leverage scoped searches instead.

Content sources and start addresses

500 hard limit

Alerts

1 million alerts on a site

Your SMTP server will probably choke a long time before you hit this limit.

Search scopes

Less than 200 per site