Consider that they can all be written as a regression equation (perhaps with slightly differing interpretations than their traditional forms).  

**Regression:**  
$$
Y=\beta_0 + \beta_1X + \varepsilon  \\
\text{where }\varepsilon\sim\mathcal N(0, \sigma^2)
$$

**t-test:**
$$
Y=\beta_0 + \beta_1X_{\text{dummy code}} + \varepsilon  \\
\text{where }\varepsilon\sim\mathcal N(0, \sigma^2)
$$

**ANOVA:**
$$
Y=\beta_0 + \beta_1X_{\text{dummy code}} + \varepsilon  \\
\text{where }\varepsilon\sim\mathcal N(0, \sigma^2)
$$

The prototypical regression is conceptualized with $X$ as a continuous variable.  However, the only assumption that is actually made about $X$ is that it is a vector of known constants.  It could be a continuous variable, but it could also be a dummy code (i.e., a vector of $0$'s & $1$'s that indicates whether an observation is a member of an indicated group--e.g., a treatment group).  Thus, in the second equation, $X$ could be such a dummy code, and the p-value would be the same as that from a t-test in its more traditional form.  

The meaning of the betas would differ here, though.  In this case, $\beta_0$ would be the mean of the control group (for which the entries in the dummy variable would be $0$'s), and $\beta_1$ would be the difference between the mean of the treatment group and the control group.  

Remember that it is perfectly reasonable to have / run an ANOVA with only two groups (although a t-test would be more common), and you have all three connected.  If you prefer, you could imagine an ANOVA with 3 groups; it would be:
$$
Y=\beta_0 + \beta_1X_{\text{dummy code 1}} + \beta_2X_{\text{dummy code 2}} + \varepsilon  \\
\text{where }\varepsilon\sim\mathcal N(0, \sigma^2)
$$
Note that when you have $g$ groups, you have $g-1$ dummy codes to represent them.  The reference group (typically the control group) is indicated by having $0$'s for *both* dummy code 1 & dummy code 2.  In this case, you would not want to interpret the p-values of the t-tests for these betas that come with standard statistical output--they only indicate whether the indicated group differs from the control group *when assessed in isolation*.  That is, these tests are not independent.