Try SearchStatus addons - for Firefox. It automatically tells you a website PageRank and Alexa rank. Here is the link to download the addon - https://addons.mozilla.org/en-US/firefox/addon/321. Hope that might help
Most of these tools do not give accurate results, so you might want to re-check the actual rankings with those provided by the tool to decide which tool to use.
Download this: http://www.cleverstat.com/google-monitor-query.htm It's free, fast, stores all your sites and keywords, checks back beyond 1,000 pages (most don't) plus shows which keywords have risen/fallen and yes it's very accurate.
Just curious, why would you use an online tool for this when you have to query each keyword/phrase individually plus re-enter them every day when you go check? It would be nearly as easy to check them in Google. Download the free program i posted, just one click and it will return your SERP's for as many keywords and phrases you enter, plus it retains your data and plots your trends.
i own a good site that will check your sites alexa, pagerank and backlinks and more.. www.checkpageranks.net
Often times that will be due to either where you are searching from, or which datacenter you are hitting. Just had a thread on that over on SEORefugee: http://www.seorefugee.com/forums/showthread.php?t=8409 Your results can depend on datacenter, ip, geolocation, and country extension of the Google you are hitting (.com, .co.uk, .ca, etc). You can use a multi dc rank checker to see where you rank on the various dc's (this one gives all results as if you are searching from the US, since that's where the tool is located): Google Multi-DC Rank Check -Michael