Link -
http://www.thinkbroadband.com/ping(Requires you to sign up for a free account to use the service)
This is a little different to most product reviews and recommendations, in that it's not really a product but a service, provided by thinkbroadband.com. I don't know how well I'm going to explain this so I would recommend reading through the info on their site, but I'll give this a go.
Basically, what this service does is ping your IP every second, and store the results - minimum latency, average latency, maximum latency, and packet loss. Doesn't sound too useful on the face of it. However, put those results onto a graph - and not just any graph, a nicely coloured one! - and you have something potentially very useful. You can see how your connection changes over time, for example if your ISP implements traffic management at peak times, or when you're downloading a lot of data you can see how that affects your latency. So, how is that useful? Well, if you seem to always have problems playing online games, you can use this to determine if your connection is always bad, or if it goes bad at certain times. If you're experiencing problems with VOIP such as Skype, perhaps your issue is high packet loss - this shouldn't happen, but if it does, the graph will show this, and give you some information so you can speak to your ISP and resolve the issue. If your connection seems much slower than it should be, well, this doesn't show your bandwidth but if your latency is consistently high, this could indicate either a congested link to your ISP, or an issue on the line. Also, because ping packets are tiny, there's nothing to worry about in terms of bandwidth usage - they quote around 70MB a month. If your IP changes, you will need to update your profile to keep the graph alive and accurate.
For an example of what the graph looks like,
click here - that's a static graph of my connection over the last 24 hours. Their FAQ section will explain in great detail how to interpret your graph, and I'm still getting used to this so I'm admittedly not the most knowledgeable, but I'll attempt to explain what this shows. I have a fairly thin green section, which doesn't spike, so I have a nice steady minimum ping, which is a good thing. The blue section also remains fairly steady, so my average latency mostly remains low, also good. You can see between 6pm and 10pm the yellow section has a general upwards trend, this could be due to me downloading a lot, or it could be traffic management in place. I know I was making fairly heavy use of my connection around those times, so this is expected. The fairly random yellow spikes are also nothing to worry about, they're a peculiarity of some routers and connections. I have no red line at the top, so no packet loss, which is great. So, in short, this shows a fairly healthy connection with no issues with high latency, packet loss, or traffic shaping - hurrah!
I probably haven't explained this all too well, but hopefully this will inspire a few of you to head over to the site and check it out. There's nothing to lose by setting it up, and once done you don't have to worry about a thing, it'll keep the graph updated and keep it online for you to view at any time, so you can look back over past days or weeks to see any changes to your connection. Again, this is on of those tools that you may never need, but is potentially a very useful source of information (and something cool to look at).