I. e. there's no need to use the inbox or external services and tools to aggregate more tags: del.icio.us does it all with "+" between the words.

In my daily dose of web-wandering I landed on a web site, The RSS cookbook, that lists and discusses a list of “10 advanced RSS tricks”.
Among these there’s a note, titled “The del.icio.us blend” where it is stated that:

“It’s easy to blend the RSS feeds for these three del.icio.us tags into one feed using Feedblendr, or alternatively you can use the del.icio.us inbox to blend the tags and then simply use the RSS feed for the entire inbox.”

Actually you don’t need to use the inbox or any external service: del.icio.us creates feeds of two or more aggregated tags just fine and this is one of the most useful feed options (which CMSes or local bookmarking in your borwser cannot do).

An example the aggregated search
http://del.icio.us/nicoladagostino/del.icio.us+strumenti
(where ‘strumenti’ is the italian word for tools)

has a corresponding feed which is
http://del.icio.us/rss/nicoladagostino/del.icio.us+strumenti

It’s simple as that! :)