For listening to conversations on Twitter about your brand, your client’s brand or anything else you need to be paying attention to online, you are literally spoiled for choice.

I think one of the simplest yet more effective tools available is Twitter search (known as Summize before Twitter acquired it), shown in the screenshot above (click for larger image).

As its name indicates, it searches tweets on the keywords you enter. Once you do that on the website, the results page tells you when new content appears on Twitter that matches your search term(s). You then manually refresh the page to see the new content. If it’s a topic many people are talking about, you’ll see update notifications literally every few seconds.

What’s especially good is the advanced search, giving you many options to zero in on the subject matter you’re interested in and who’s talking about it.

Equally good is how you can subscribe to an RSS feed of your particular search, which means you can sit back and wait for the results to come to you.

New on the scene is Tweetag, a search tool that provides some very useful additional dimensions to your Twitter listening.

Not only does it return results based on key words and phrases you search for (as Twitter search does), but also suggests other related key words and phrase, what it calls tags.

So an experiment in searching Tweetag for ‘motrin’ – unquestionably a very hot topic this week – produced a list of tweets as I would expect, but additionally a range of possibly related tags as the screenshot shows (click for larger image).

You then click on a tag that interests you to see a new page showing you tweets of that tag as well as from your original search term. This could be useful from a granularity perspective.

Tweetag doesn’t have an RSS option as Twitter search does. But it does offer Share This, meaning you can share the content on your social networks as well as to your Friendfeed account, email it, even post it on your blog.

Deaxon, the Brussels-based developer of Tweetag, also offer an API, meaning that if you’re a developer, you could do something like integrate Tweetag within Twitter applications to allow users to monitor any rising trend about any given topic.

I’ve started using Tweetag as a complementary listening tool to Twitter search. If you’re paying attention to who’s saying what on Twitter, you might want to do the same.

(Tweetag spotted via TechCrunch.)