I just made the sealevel R package, which we used for the sea-level rise articles, available. It provides some functions to quickly download, read and analyse the global tide gauges and satellite data.
All suggestions, patches, comments are welcome. This package is part of OpenEarth but available through r-forge for the convenience of R users.

Example

The code below generates the plot of the Dutch tide gauges. 

# install.packages("sealevel", repos="http://r-forge.r-project.org")
library(sealevel)
library(ggplot2)
library(plyr)

# Load the Dutch sealevel data
data(dutch)

# Let's plot them all

# The stations are a list of objects, but we can make a data frame like this
station2df <- function(x){
  df <- x$data
  df$name <- x$name
  # set -999 to missing
  df$waterlevel[df$waterlevel==-999.9] <- NA
  return(df)
}

# Let's do bit of map reducing, list -> station2df -> data.frame
dutchdf <- ldply(dutch, station2df)
# Now make a factor instead from the strings
dutchdf$name <- as.factor(dutchdf$name)
# so we can use it to shift the waterlevels a bit
dutchdf$waterlevel <- dutchdf$waterlevel - as.numeric(dutchdf$name)*10

# Use the gramar of graphics approach
p <- ggplot(dutchdf, aes(year, waterlevel, color=name))
# Fit a nodal cycle (long term tide), See Baart et al 2012 in JCR. 
p + geom_point() + geom_smooth(method='lm', formula=y~x+I(cos(2*pi*x/18.613))+I(sin(2*pi*x/18.613)))

Notice that after the last 6 years of (average) sea-level decline we are about to see a rising sea level at the Dutch coast again for the next 12 years.