Anyone working in Search Engine Marketing knows that this industry travels at warp speed. If you're trying to market your web site or the web sites of your clients via search engines, chances are your time is limited - severely limited.

To squeeze as much into my schedule as possible without resorting to self-cloning, my daily routine involves the use of a range of time-saving tools and software. I use such tools on a daily basis and I truly don't know how I'd function without them. I'm not the only one. I've talked to other SEM experts and they also rely on various tools to help them through their hectic schedules.

Here is a líst of 20 must-have tools used by busy SEM professionals:

1. Freshbooks Invoicing and Timesheets
Freshbooks is an online estimating, invoicing, project management and time tracking service that gives your business a professional image, no matter how small. I use it to invoice all my clients online and it can even be set up to automatically bill and debit the credít cards of recurring clients every month. It also has built in staff timesheets and project management tools for online collaboration.

Price: Free for 3 clients or less

2. XML Sitemaps Generator
The XML Sitemap Generator trawls through all levels of your site to generate an XML sitemap. It also gives you a running count of pages, provides a text-based URL líst and a HTML sitemap you can import straight into your site. The online version of the generator is free for sites of less than 500 pages, but there's also a low-cost script-based version for large sites that can be set up to automatically index your site, upload an updated XML file to your server and ping Google and Yahoo when done.

Price: Free for sites of 500 pages or less

3. Proposal Kit
ProposalKit takes the chore out of creating and tailoring client estimates and proposal contracts. With over 200 pre-designed self-guiding templates ready to fill in the blanks with your company, project/product/service and client information, ProposalKit has already half completed your proposal for you.

Price: From USD 47.00

4. ClickTracks
As far as site analytics goes, the depth and accuracy of data provided by ClickTracks just can't be beaten, in my opinion. The visual analysis ClickTracks provides is probably its best known feature, with statistical data overlaying actual screenshots of your web site pages. The ability to flag individual visitors or groups of visitors based on unique identifiers (such as all persons who visited page x or all persons who bought product d) provides a level of analysis that other analytical packages can't compete with.

Price: From USD 79.00 per month

5. AWeber
AWeber is a multiple auto responder and mailing líst management service rolled into one. Members can send an unlimited number of campaigns, follow up messages, and newsletters to an unlimited number of approved opt-ín lists. For newsletter purposes, a wide range of templates are provided, as are free training guides and videos to help you create campaigns.

Price: From USD 19.95 per month

6. JROX
JROX Affilíate Manager software (JAM) is a super powerful affilíate program that includes follow up email tools, email broadcasting, custom URLs and the ability to create up to 10 affilíate downlink levels. It offers affiliates groovy 3d Flash-based graphs and charts displaying their referrals and commissions and an organized marketing tools area for storage of banners, links and promotional materials.

Price: Free for 50 affiliates or less

7. Keyword Discovery
Keyword Discovery is an advanced keyword research and search term suggestion tool produced by Trellian.

Price: From USD 69.95 per month

8. Google Analytics
Google Analytics is free web-based site metrics / analytics software hosted by Google. After you include tracking code on all selected pages of your site, Google collects data regarding visitor activity and then you are able to log into an Analytics interface and view site activity and produce reports.

Price: $0

9) Backlinkwatch.com
Type your URL into Backlink Watch and get complete detailed information about the quality and quantity of backward links pointing to your website. It will show you anchor text, Google Toolbar PageRank, total outbound links on that page and nofollow flag for each of your inbound links available.

Price: $0

10) Jim Boykin's tools
A collection of 17 free SEO tools developed by Jim Boykin and his staff, including a cache analyzer, Backlink checker, keyword density tool and multiple inbound and outbound link checking tools.

Price: $0

11) Google Webmaster Central
Google Webmaster Central is Google's one-stop shop for webmaster resources. It contains answers to common questíons about Google crawling and indexing and guidelines for webmasters to follow when publishing their content. It also provides statistics, diagnostics and management of Google's indexing of your website, including Sitemap submission and reporting.

Price: $0

12) Yahoo! Site Explorer
Yahoo! Site Explorer is Yahoo's version of Google Webmaster Tools. It allows you to explore all the web pages indexed by Yahoo! Search, view the most popular pages from any site, view a comprehensive site map and find pages that link to that site or any page.

Price: $0

13) Ranks.nl
Ranks.nl is a keyword density and page prominence indicator. Type in a URL and target keywords to determine the page density and prominence for certain keywords within the page text and/or HTML tags.

Price: $0

14) Rex Swain's Tools
Rex Swain is an independent software developer who has uploaded a range of his custom server tools and demos to his web site. Tools include an RGB color sampler, HTTP Cookie Demo, a HTML sampler and an email form demo.

Price: $0

15) SearchStatus for Firefox
SearchStatus is a toolbar extension for Firefox and Mozilla that allows you to see how any and every website in the world is performing in the search engines.

Price: $0

16) Microsoft Excel
Microsoft Excel is probably the world's most popular spreadsheet application. Apart from its powerful formulas for financial reporting, Excel charts and spreadsheets are great for site analytics analysis and sharing, sitemap creation, SEO/PPC campaign reporting and tracking link building campaigns.

Price: Bundled with MS Office from USD 180.00

17) Google Reader
Google Reader is a RSS and XML feed reader that constantly checks your favorite news sites and blogs for new content and presents them to you in one interface. It also allows you to share sites/pages of interest with others.

Price: $0

18) Blogger
Blogger is a popular online blog provider and templating service owned by Google, where you can quickly set up a blog of your own to post thoughts, interact with people, and more.

Price: $0

19) The Lynx Viewer
The Lynx Viewer developed by YellowPipe allows webmasters to see what their pages will look like when viewed with Lynx, a text-mode web browser. This view is very similar to how search engine robots see your site.

Price: $0

20) Basecamp
Basecamp is an online collaboration and project management service designed for staff and clients to manage internal and client projects from multiple locations.

Price: Free for 1 project

So there you have it - 20 of the most popular time-saving tools to help you with your search engine marketing efforts.